From cf4d02b49bc9c4ac7b6c58fa48e64bd25f13e85c Mon Sep 17 00:00:00 2001
From: Linus Rath <139418639+rathlinus@users.noreply.github.com>
Date: Thu, 29 Oct 2026 15:33:34 +0100
Subject: [PATCH] feat: draw calendar, tag and folder colours in a
 colour-blind-safe palette when that setting is on

---
 .../calendar/__tests__/event-card.test.tsx    |  16 +++
 components/calendar/calendar-agenda-view.tsx  |   4 +-
 components/calendar/calendar-day-view.tsx     |   4 +-
 components/calendar/calendar-month-view.tsx   |  10 +-
 components/calendar/calendar-search.tsx       |   4 +-
 .../calendar/calendar-sidebar-panel.tsx       |   4 +-
 components/calendar/calendar-toolbar.tsx      |   6 +-
 components/calendar/calendar-week-view.tsx    |   6 +-
 components/calendar/event-card.tsx            |   4 +-
 components/calendar/event-detail-popover.tsx  |   4 +-
 components/calendar/event-modal.tsx           |   4 +-
 components/calendar/quick-create-popover.tsx  |   4 +-
 components/calendar/task-chip.tsx             |   4 +-
 components/calendar/task-list-view.tsx        |   4 +-
 components/layout/mv-side-panel.tsx           |   4 +-
 components/layout/sidebar.tsx                 |  21 +--
 hooks/__tests__/use-keyword-format.test.tsx   |  15 ++
 hooks/use-cvd-color.ts                        |  13 ++
 hooks/use-keyword-format.ts                   |  16 ++-
 lib/__tests__/cvd-palette.test.ts             |  51 +++++++
 lib/cvd-palette.ts                            | 129 ++++++++++++++++++
 21 files changed, 295 insertions(+), 32 deletions(-)
 create mode 100644 hooks/use-cvd-color.ts
 create mode 100644 lib/__tests__/cvd-palette.test.ts
 create mode 100644 lib/cvd-palette.ts

diff --git a/components/calendar/__tests__/event-card.test.tsx b/components/calendar/__tests__/event-card.test.tsx
index 2d76501b7..e9e7b2616 100644
--- a/components/calendar/__tests__/event-card.test.tsx
+++ b/components/calendar/__tests__/event-card.test.tsx
@@ -112,3 +112,19 @@ describe('EventCard fill', () => {
     });
   });
 });
+
+describe('EventCard colour settings', () => {
+  const calendar = { id: 'cal-1', name: 'Work', color: '#22c55e' } as unknown as Calendar;
+  afterEach(() => {
+    cleanup();
+    useSettingsStore.setState({ showColorNames: false, colorBlindPalette: false });
+  });
+
+  it("draws the event in the colour-blind-safe colour and keeps the calendar's own", () => {
+    useSettingsStore.setState({ colorBlindPalette: true });
+    render(<EventCard event={makeOccurrence('a', 'accepted')} calendar={calendar} variant="block" currentUserEmails={me} />);
+    // #009E73, the palette's bluish green
+    expect(screen.getByRole('button').style.backgroundColor).toBe('rgb(0, 158, 115)');
+    expect(calendar.color).toBe('#22c55e');
+  });
+});
diff --git a/components/calendar/calendar-agenda-view.tsx b/components/calendar/calendar-agenda-view.tsx
index e453d8bac..2300525f9 100644
--- a/components/calendar/calendar-agenda-view.tsx
+++ b/components/calendar/calendar-agenda-view.tsx
@@ -15,6 +15,7 @@ import { getParticipantCount, isDeclinedByUser } from "@/lib/calendar-participan
 import { useScrollWindow } from "@/hooks/use-scroll-window";
 import type { ScrollWindowViewProps } from "@/lib/calendar-scroll-window";
 import type { CalendarEvent, Calendar } from "@/lib/jmap/types";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarAgendaViewProps extends ScrollWindowViewProps {
   events: CalendarEvent[];
@@ -55,6 +56,7 @@ export function CalendarAgendaView({
   onCreateEvent,
 }: CalendarAgendaViewProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   // Grid days / event dates are display dates (local fields = wall-clock in
   // the user's zone); the app-wide formatter would shift them again (#755).
   const intlFormatter = useDisplayDateFormatter();
@@ -240,7 +242,7 @@ export function CalendarAgendaView({
             {group.events.map((ev) => {
               const calId = getPrimaryCalendarId(ev);
               const calendar = calId ? calendarMap.get(calId) : undefined;
-              const color = getEventColor(ev, calendar);
+              const color = paint(getEventColor(ev, calendar));
               const start = getEventStartDate(ev);
               const end = getEventEndDate(ev);
               // iTIP CANCEL marks the attendee's copy with status "cancelled"
diff --git a/components/calendar/calendar-day-view.tsx b/components/calendar/calendar-day-view.tsx
index feb5f531c..a1d64f7d0 100644
--- a/components/calendar/calendar-day-view.tsx
+++ b/components/calendar/calendar-day-view.tsx
@@ -23,6 +23,7 @@ import { dayKey, type ScrollWindowViewProps } from "@/lib/calendar-scroll-window
 import type { PendingEventPreview } from "./event-modal";
 import { useCalendarErrorMessage } from "@/hooks/use-calendar-error-message";
 import { PluginDayLabel } from "./plugin-day-label";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarDayViewProps extends ScrollWindowViewProps {
   selectedDate: Date;
@@ -93,6 +94,7 @@ export function CalendarDayView({
   revealAt,
 }: CalendarDayViewProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tintedEvents = useSettingsStore((s) => s.calendarTintedEvents);
   const describeError = useCalendarErrorMessage();
   // Grid days / event dates are display dates (local fields = wall-clock in
@@ -649,7 +651,7 @@ export function CalendarDayView({
                         if (startMin + durationMin <= hours.startMinutes || startMin >= hours.endMinutes) return null;
                         const clip = clipToDisplayHours(startMin, startMin + durationMin, hours);
                         const cal = calendars.find(c => c.id === pendingPreview.calendarId);
-                        const color = cal?.color || "#3b82f6";
+                        const color = paint(cal?.color || "#3b82f6");
                         // Drawn like a saved event, so the new event shows where
                         // it will land while it is being created.
                         return (
diff --git a/components/calendar/calendar-month-view.tsx b/components/calendar/calendar-month-view.tsx
index a29f88daf..e0da8549c 100644
--- a/components/calendar/calendar-month-view.tsx
+++ b/components/calendar/calendar-month-view.tsx
@@ -23,6 +23,7 @@ import { useCalendarErrorMessage } from "@/hooks/use-calendar-error-message";
 import { PluginDayLabel } from "./plugin-day-label";
 import { useDisplayDateFormatter } from "@/hooks/use-display-date-formatter";
 import type { MoveEventHandler } from "@/hooks/use-time-grid-interactions";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarMonthViewProps extends ScrollWindowViewProps {
   selectedDate: Date;
@@ -94,6 +95,7 @@ export function CalendarMonthView({
   onMoveEvent,
 }: CalendarMonthViewProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const describeError = useCalendarErrorMessage();
   const showTimeInMonthView = useSettingsStore((state) => state.showTimeInMonthView);
   // On mobile the month view collapses events to dots unless the user opted
@@ -469,7 +471,7 @@ export function CalendarMonthView({
                       {dayEvents.slice(0, 3).map((ev) => {
                         const calId = getPrimaryCalendarId(ev);
                         const cal = calId ? calendarMap.get(calId) : undefined;
-                        const evColor = ev.color || cal?.color || "#3b82f6";
+                        const evColor = paint(ev.color || cal?.color || "#3b82f6");
                         const inactive = ev.status === "cancelled" || isDeclinedByUser(ev, currentUserEmails);
                         return (
                           <span
@@ -487,7 +489,7 @@ export function CalendarMonthView({
                             key={`task-${task.id}`}
                             data-calendar-task={task.id}
                             className={cn("w-1.5 h-1.5 rounded-full border", task.progress === "completed" && "opacity-40")}
-                            style={{ borderColor: (calId && calendarMap.get(calId)?.color) || "#3b82f6" }}
+                            style={{ borderColor: paint((calId && calendarMap.get(calId)?.color) || "#3b82f6") }}
                           />
                         );
                       })}
@@ -497,7 +499,7 @@ export function CalendarMonthView({
                       {pendingPreview && checkIsSameDay(pendingPreview.start, day) && (
                         <span
                           className="w-1.5 h-1.5 rounded-full border border-dashed"
-                          style={{ borderColor: calendarMap.get(pendingPreview.calendarId)?.color || "#3b82f6" }}
+                          style={{ borderColor: paint(calendarMap.get(pendingPreview.calendarId)?.color || "#3b82f6") }}
                         />
                       )}
                     </div>
@@ -512,7 +514,7 @@ export function CalendarMonthView({
               if (previewDayIdx === -1) return null;
               const previewRow = Math.max(rowCount, dayEventRows[previewDayIdx] + dayTasks[previewDayIdx].length);
               const cal = calendarMap.get(pendingPreview.calendarId);
-              const color = cal?.color || "#3b82f6";
+              const color = paint(cal?.color || "#3b82f6");
               return (
                 <div className="absolute inset-x-0 pointer-events-none" style={{ top: overlayTop }}>
                   <div
diff --git a/components/calendar/calendar-search.tsx b/components/calendar/calendar-search.tsx
index 5de72dfab..84f9ec060 100644
--- a/components/calendar/calendar-search.tsx
+++ b/components/calendar/calendar-search.tsx
@@ -17,6 +17,7 @@ import { displayNow } from "@/lib/timezone";
 import type { Calendar, CalendarEvent } from "@/lib/jmap/types";
 import type { CalendarSearchResults as Results } from "@/hooks/use-calendar-event-search";
 import { getEventColor } from "./event-card";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 const RESULT_SELECTOR = "[data-search-result]";
 
@@ -83,6 +84,7 @@ export function CalendarSearchResults({
   query, results, calendars, timeFormat = "24h", currentUserEmails, onSelectEvent, onContextMenuEvent, onClearSearch,
 }: CalendarSearchResultsProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const intlFormatter = useDisplayDateFormatter();
   const listRef = useRef<HTMLDivElement>(null);
   const calendarMap = useMemo(() => new Map(calendars.map((c) => [c.id, c])), [calendars]);
@@ -108,7 +110,7 @@ export function CalendarSearchResults({
   const renderRow = (ev: CalendarEvent) => {
     const calId = getPrimaryCalendarId(ev);
     const calendar = calId ? calendarMap.get(calId) : undefined;
-    const color = getEventColor(ev, calendar);
+    const color = paint(getEventColor(ev, calendar));
     const start = getEventStartDate(ev);
     const end = getEventEndDate(ev);
     const isInactive = ev.status === "cancelled" || isDeclinedByUser(ev, currentUserEmails);
diff --git a/components/calendar/calendar-sidebar-panel.tsx b/components/calendar/calendar-sidebar-panel.tsx
index 8f3ba4343..9ebc0c85d 100644
--- a/components/calendar/calendar-sidebar-panel.tsx
+++ b/components/calendar/calendar-sidebar-panel.tsx
@@ -23,6 +23,7 @@ import type { IJMAPClient } from '@/lib/jmap/client-interface';
 import { displayNow } from "@/lib/timezone";
 import { readableTextOn } from "@/lib/color-transform";
 import { shareRecipientNames, useShareRecipientLabels } from "@/hooks/use-share-recipient-labels";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 /**
  * Split a per-account calendar list into "owned" (the user's own) and
@@ -92,6 +93,7 @@ export function CalendarSidebarPanel({
   multiAccountMode,
 }: CalendarSidebarPanelProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tSub = useTranslations("calendar.subscription");
   const tMgmt = useTranslations("calendar.management");
   const isSubscriptionCalendar = useCalendarStore((s) => s.isSubscriptionCalendar);
@@ -277,7 +279,7 @@ export function CalendarSidebarPanel({
 
   const renderCalendarItem = (cal: Calendar) => {
     const isVisible = selectedCalendarIds.includes(cal.id);
-    const color = cal.color || "#3b82f6";
+    const color = paint(cal.color || "#3b82f6");
     const hasMenu = isSubscriptionCalendar(cal.id) ? !!client : true;
 
     return (
diff --git a/components/calendar/calendar-toolbar.tsx b/components/calendar/calendar-toolbar.tsx
index 7763420d6..69a6ef7ee 100644
--- a/components/calendar/calendar-toolbar.tsx
+++ b/components/calendar/calendar-toolbar.tsx
@@ -15,6 +15,7 @@ import type { CalendarViewMode } from "@/stores/calendar-store";
 import type { Calendar } from "@/lib/jmap/types";
 import { useCalendarLocale } from "@/hooks/use-calendar-locale";
 import { displayNow } from "@/lib/timezone";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarToolbarProps {
   selectedDate: Date;
@@ -102,6 +103,7 @@ export function CalendarToolbar({
   onCloseSearch,
 }: CalendarToolbarProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tCommon = useTranslations("common");
   const {
     weekStartsOn,
@@ -316,7 +318,7 @@ export function CalendarToolbar({
                       <div className="space-y-0.5">
                         {calendars.filter(c => !c.isShared).map((cal) => {
                           const isVisible = selectedCalendarIds.includes(cal.id);
-                          const color = cal.color || "#3b82f6";
+                          const color = paint(cal.color || "#3b82f6");
                           return (
                             <button
                               key={cal.id}
@@ -356,7 +358,7 @@ export function CalendarToolbar({
                             <div className="space-y-0.5">
                               {group.cals.map((cal) => {
                                 const isVisible = selectedCalendarIds.includes(cal.id);
-                                const color = cal.color || "#3b82f6";
+                                const color = paint(cal.color || "#3b82f6");
                                 return (
                                   <button
                                     key={cal.id}
diff --git a/components/calendar/calendar-week-view.tsx b/components/calendar/calendar-week-view.tsx
index 33ca71554..946b2ca9b 100644
--- a/components/calendar/calendar-week-view.tsx
+++ b/components/calendar/calendar-week-view.tsx
@@ -25,6 +25,7 @@ import { dayKey, type ScrollWindowViewProps } from "@/lib/calendar-scroll-window
 import type { PendingEventPreview } from "./event-modal";
 import { useCalendarErrorMessage } from "@/hooks/use-calendar-error-message";
 import { PluginDayLabel } from "./plugin-day-label";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarWeekViewProps extends ScrollWindowViewProps {
   selectedDate: Date;
@@ -106,6 +107,7 @@ export function CalendarWeekView({
   revealAt,
 }: CalendarWeekViewProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tintedEvents = useSettingsStore((s) => s.calendarTintedEvents);
   const describeError = useCalendarErrorMessage();
   // Grid days / event dates are display dates (local fields = wall-clock in
@@ -575,7 +577,7 @@ export function CalendarWeekView({
             {pendingPreview?.allDay && (() => {
               const index = days.findIndex((d) => isSameDay(d, pendingPreview.start));
               if (index === -1) return null;
-              const color = calendars.find((c) => c.id === pendingPreview.calendarId)?.color || "#3b82f6";
+              const color = paint(calendars.find((c) => c.id === pendingPreview.calendarId)?.color || "#3b82f6");
               return (
                 <div
                   data-pending-preview
@@ -833,7 +835,7 @@ export function CalendarWeekView({
                       if (startMin + durationMin <= hours.startMinutes || startMin >= hours.endMinutes) return null;
                       const clip = clipToDisplayHours(startMin, startMin + durationMin, hours);
                       const cal = calendars.find(c => c.id === pendingPreview.calendarId);
-                      const color = cal?.color || "#3b82f6";
+                      const color = paint(cal?.color || "#3b82f6");
                       // Drawn like a saved event, so the new event shows where
                       // it will land while it is being created.
                       return (
diff --git a/components/calendar/event-card.tsx b/components/calendar/event-card.tsx
index d2b1b3efa..7bd91f642 100644
--- a/components/calendar/event-card.tsx
+++ b/components/calendar/event-card.tsx
@@ -11,6 +11,7 @@ import { getEventEndDate, getEventStartDate } from "@/lib/calendar-utils";
 import { useSettingsStore } from "@/stores/settings-store";
 import { readableTextOn } from "@/lib/color-transform";
 import { useLongPress } from "@/hooks/use-long-press";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface EventCardProps {
   event: CalendarEvent;
@@ -117,7 +118,8 @@ function createEventDragPreview(title: string, timeRange: string, color: string)
 export function EventCard({ event, calendar, variant, onClick, onMouseEnter, onMouseLeave, onContextMenu, isSelected, draggable: isDraggable, continuesBefore = false, continuesAfter = false, className, style, currentUserEmails, tabbable = true }: EventCardProps) {
   const t = useTranslations("calendar");
   const [isBeingDragged, setIsBeingDragged] = useState(false);
-  const color = getEventColor(event, calendar);
+  const paint = useCvdColor();
+  const color = paint(getEventColor(event, calendar));
   const startDate = getEventStartDate(event);
   const timeFormat = useSettingsStore((state) => state.timeFormat);
   const showTimeInMonthView = useSettingsStore((state) => state.showTimeInMonthView);
diff --git a/components/calendar/event-detail-popover.tsx b/components/calendar/event-detail-popover.tsx
index ed44ea0ed..d9b30d3ed 100644
--- a/components/calendar/event-detail-popover.tsx
+++ b/components/calendar/event-detail-popover.tsx
@@ -32,6 +32,7 @@ import { eventToView } from "@/lib/plugin-projection";
 import { ParticipantStatusBadge, RsvpButtons } from "./rsvp-buttons";
 import { isEditableEventTarget } from "@/lib/keyboard";
 import { isSingleKeyShortcutOff } from "@/lib/single-key-shortcuts";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface EventDetailPopoverProps {
   event: CalendarEvent;
@@ -140,6 +141,7 @@ export function EventDetailPopover({
   pinned = false,
 }: EventDetailPopoverProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tCommon = useTranslations("common");
   const locale = useLocale();
   const popoverRef = useRef<HTMLDivElement>(null);
@@ -154,7 +156,7 @@ export function EventDetailPopover({
   // render with the contact card's name instead of the raw email.
   const resolveContactName = useContactNameResolver();
 
-  const color = getEventColor(event, calendar);
+  const color = paint(getEventColor(event, calendar));
   const startDate = getEventStartDate(event);
   const durationMinutes = parseDuration(event.duration);
   const endDate = getEventEndDate(event);
diff --git a/components/calendar/event-modal.tsx b/components/calendar/event-modal.tsx
index c68bf2d5a..ff3dac654 100644
--- a/components/calendar/event-modal.tsx
+++ b/components/calendar/event-modal.tsx
@@ -50,6 +50,7 @@ import { eventToView } from "@/lib/plugin-projection";
 import { ConfirmDialog } from "@/components/ui/confirm-dialog";
 import { useConfirmDialog } from "@/hooks/use-confirm-dialog";
 import { useFocusTrap } from "@/hooks/use-focus-trap";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 export interface PendingEventPreview {
   start: Date;
@@ -267,6 +268,7 @@ export function EventModal({
   isMobile = false,
 }: EventModalProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tCommon = useTranslations("common");
   const locale = useLocale();
   const timeFormat = useSettingsStore((s) => s.timeFormat);
@@ -988,7 +990,7 @@ export function EventModal({
     const recurrenceLabel = getRecurrenceLabel(event, t, locale);
     const alertLabel = formatEventAlertsLabel(event, calendars, t);
     const eventCalendar = calendars.find(c => event.calendarIds[c.id]);
-    const color = getEventColor(event, eventCalendar);
+    const color = paint(getEventColor(event, eventCalendar));
 
     return (
       <div ref={modalRef} role="dialog" aria-modal={isMobile || undefined} aria-label={event.title || t("events.no_title")} className={isMobile ? mobileRootClass : "flex flex-col h-full bg-background"}>
diff --git a/components/calendar/quick-create-popover.tsx b/components/calendar/quick-create-popover.tsx
index bbb7fac19..d20038e90 100644
--- a/components/calendar/quick-create-popover.tsx
+++ b/components/calendar/quick-create-popover.tsx
@@ -10,6 +10,7 @@ import { Clock, X } from "@/components/icons";
 import { IconButton } from "@/components/ui/icon-button";
 import type { Calendar } from "@/lib/jmap/types";
 import { useDisplayDateFormatter } from "@/hooks/use-display-date-formatter";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 export interface QuickCreateDraft {
   start: Date;
@@ -66,6 +67,7 @@ export function QuickCreatePopover({
   onClose,
 }: QuickCreatePopoverProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const tCommon = useTranslations("common");
   const intlFormatter = useDisplayDateFormatter();
   const ref = useRef<HTMLDivElement>(null);
@@ -189,7 +191,7 @@ export function QuickCreatePopover({
             <div className="flex items-center gap-2.5">
               <span
                 className="w-4 h-4 rounded-sm flex-shrink-0"
-                style={{ backgroundColor: calendars.find((c) => c.id === draft.calendarId)?.color || "#3b82f6" }}
+                style={{ backgroundColor: paint(calendars.find((c) => c.id === draft.calendarId)?.color || "#3b82f6") }}
                 aria-hidden="true"
               />
               <select
diff --git a/components/calendar/task-chip.tsx b/components/calendar/task-chip.tsx
index 73f581559..3b46d340e 100644
--- a/components/calendar/task-chip.tsx
+++ b/components/calendar/task-chip.tsx
@@ -4,6 +4,7 @@ import { useTranslations } from "next-intl";
 import { cn } from "@/lib/utils";
 import { Check } from "@/components/icons";
 import type { Calendar, CalendarTask } from "@/lib/jmap/types";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface CalendarTaskChipProps {
   task: CalendarTask;
@@ -23,8 +24,9 @@ interface CalendarTaskChipProps {
  */
 export function CalendarTaskChip({ task, calendar, onToggleComplete, onSelect, touch = false, tabbable = true, className }: CalendarTaskChipProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const isCompleted = task.progress === "completed";
-  const color = calendar?.color || "#3b82f6";
+  const color = paint(calendar?.color || "#3b82f6");
   const title = task.title || t("tasks.no_title");
 
   return (
diff --git a/components/calendar/task-list-view.tsx b/components/calendar/task-list-view.tsx
index 2ddf2ecf7..e6672273c 100644
--- a/components/calendar/task-list-view.tsx
+++ b/components/calendar/task-list-view.tsx
@@ -10,6 +10,7 @@ import type { CalendarTask, Calendar } from "@/lib/jmap/types";
 import type { TaskViewFilter } from "@/stores/task-store";
 import { useSettingsStore } from "@/stores/settings-store";
 import { useDisplayDateFormatter } from "@/hooks/use-display-date-formatter";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 interface TaskListViewProps {
   tasks: CalendarTask[];
@@ -125,6 +126,7 @@ export function TaskListView({
   onQuickCreate,
 }: TaskListViewProps) {
   const t = useTranslations("calendar");
+  const paint = useCvdColor();
   const timeFormat = useSettingsStore((s) => s.timeFormat);
   const { dateTime: formatDate } = useDisplayDateFormatter();
   const [quickAddTitle, setQuickAddTitle] = useState("");
@@ -249,7 +251,7 @@ export function TaskListView({
                   )}
                   {cal && (
                     <span className="text-xs text-muted-foreground flex items-center gap-1">
-                      <span className="w-2 h-2 rounded-full flex-shrink-0" style={{ backgroundColor: cal.color || "#3b82f6" }} />
+                      <span className="w-2 h-2 rounded-full flex-shrink-0" style={{ backgroundColor: paint(cal.color || "#3b82f6") }} />
                       {cal.name}
                     </span>
                   )}
diff --git a/components/layout/mv-side-panel.tsx b/components/layout/mv-side-panel.tsx
index 2a61cd326..25af90a61 100644
--- a/components/layout/mv-side-panel.tsx
+++ b/components/layout/mv-side-panel.tsx
@@ -26,6 +26,7 @@ import { requestInternalMailto } from "@/lib/protocol-handlers/mailto";
 import { formatDateTime, cn } from "@/lib/utils";
 import { Avatar } from "@/components/ui/avatar";
 import type { CalendarEvent } from "@/lib/jmap/types";
+import { useCvdColor } from "@/hooks/use-cvd-color";
 
 export type MvSidePanelId = "calendar" | "tasks" | "contacts";
 
@@ -171,9 +172,10 @@ function CalendarPanel({ onClose }: { onClose: () => void }) {
     if (scrollRef.current) scrollRef.current.scrollTop = hour * HOUR_PX;
   }, [day]);
 
+  const paint = useCvdColor();
   const colorOf = (event: CalendarEvent) => {
     const calId = Object.keys(event.calendarIds ?? {})[0];
-    return event.color || calendars.find((c) => c.id === calId)?.color || "var(--color-primary)";
+    return paint(event.color || calendars.find((c) => c.id === calId)?.color || "var(--color-primary)");
   };
 
   const visible = events.filter((e) => {
diff --git a/components/layout/sidebar.tsx b/components/layout/sidebar.tsx
index a57a0d722..333eebf49 100644
--- a/components/layout/sidebar.tsx
+++ b/components/layout/sidebar.tsx
@@ -195,17 +195,20 @@ const getIconForMailbox = (role?: string, hasChildren?: boolean, isExpanded?: bo
 
 // Role tints from the theme's tokens (R11), so a theme recolours them and
 // dark mode has its own values: the chart palette for the main roles.
+// With colour-blind-safe colours on (<html data-cvd-palette="on">) each
+// colour is swapped for one of the palette in lib/cvd-palette.ts. Written
+// out in full so Tailwind generates the classes.
 const ROLE_ICON_COLOR: Record<string, string> = {
-  inbox: "text-chart-1/80",
-  sent: "text-chart-2/80",
-  drafts: "text-chart-5/80",
+  inbox: "text-chart-1/80 [[data-cvd-palette=on]_&]:text-[#0072B2]",
+  sent: "text-chart-2/80 [[data-cvd-palette=on]_&]:text-[#009E73]",
+  drafts: "text-chart-5/80 [[data-cvd-palette=on]_&]:text-[#CC79A7]",
   trash: "text-muted-foreground",
-  junk: "text-chart-4/80",
-  archive: "text-chart-3/80",
-  shared: "text-info/80",
-  important: "text-warning/80",
-  memos: "text-warning/80",
-  scheduled: "text-info/80",
+  junk: "text-chart-4/80 [[data-cvd-palette=on]_&]:text-[#D55E00]",
+  archive: "text-chart-3/80 [[data-cvd-palette=on]_&]:text-[#56B4E9]",
+  shared: "text-info/80 [[data-cvd-palette=on]_&]:text-[#F0E442]",
+  important: "text-warning/80 [[data-cvd-palette=on]_&]:text-[#E69F00]",
+  memos: "text-warning/80 [[data-cvd-palette=on]_&]:text-[#E69F00]",
+  scheduled: "text-info/80 [[data-cvd-palette=on]_&]:text-[#F0E442]",
   snoozed: "text-muted-foreground",
 };
 
diff --git a/hooks/__tests__/use-keyword-format.test.tsx b/hooks/__tests__/use-keyword-format.test.tsx
index bbc919d16..1f94203cc 100644
--- a/hooks/__tests__/use-keyword-format.test.tsx
+++ b/hooks/__tests__/use-keyword-format.test.tsx
@@ -16,6 +16,21 @@ describe('useKeywordFormat', () => {
   });
 
   describe('tagColor', () => {
+    it('draws tags in the colour-blind-safe palette while that setting is on', () => {
+      useSettingsStore.setState({ colorBlindPalette: true });
+      try {
+        const { result } = renderHook(() => useKeywordFormat());
+        // Blue and green, which red-green colour blindness can confuse, land on
+        // the palette's blue and bluish green; the stored colours stay.
+        expect(result.current.tagColor('work').dot).toBe('bg-[#0072B2]');
+        expect(result.current.tagColor('work/clients').dot).toBe('bg-[#009E73]');
+        expect(result.current.tagColor('archive').dot).toBe('bg-[#D55E00]');
+        expect(useSettingsStore.getState().emailKeywords[0].color).toBe('blue');
+      } finally {
+        useSettingsStore.setState({ colorBlindPalette: false });
+      }
+    });
+
     it('resolves a tag to its palette entry, including the new shades', () => {
       const { result } = renderHook(() => useKeywordFormat());
 
diff --git a/hooks/use-cvd-color.ts b/hooks/use-cvd-color.ts
new file mode 100644
index 000000000..c879d7f49
--- /dev/null
+++ b/hooks/use-cvd-color.ts
@@ -0,0 +1,13 @@
+import { useCallback } from "react";
+import { useSettingsStore } from "@/stores/settings-store";
+import { cvdColor } from "@/lib/cvd-palette";
+
+/**
+ * Maps a stored colour (calendar, event) to the colour it is drawn in: the
+ * colour-blind-safe one when that setting is on, else itself. The stored
+ * colour never changes.
+ */
+export function useCvdColor(): (color: string) => string {
+  const enabled = useSettingsStore((s) => s.colorBlindPalette);
+  return useCallback((color: string) => cvdColor(color, enabled), [enabled]);
+}
diff --git a/hooks/use-keyword-format.ts b/hooks/use-keyword-format.ts
index 3d44c934b..60021e98a 100644
--- a/hooks/use-keyword-format.ts
+++ b/hooks/use-keyword-format.ts
@@ -10,6 +10,7 @@ import {
 import { formatKeyword, formatKeywordLabels, keywordRenderings } from "@/lib/keyword-format";
 import { suggestKeywordColor } from "@/lib/keyword-discovery";
 import { useAccountTags, type TagScope } from "@/hooks/use-account-tags";
+import { CVD_CLASSES, cvdHue } from "@/lib/cvd-palette";
 
 /**
  * Names and colours tags for the screen, bound to the user's tag settings.
@@ -27,6 +28,7 @@ import { useAccountTags, type TagScope } from "@/hooks/use-account-tags";
 export function useKeywordFormat(scope?: TagScope | null) {
   const keywords = useAccountTags(scope).definitions;
   const nested = useSettingsStore((state) => state.nestedTags);
+  const colorBlindPalette = useSettingsStore((state) => state.colorBlindPalette);
 
   return useMemo(
     () => ({
@@ -50,9 +52,15 @@ export function useKeywordFormat(scope?: TagScope | null) {
        * the proposal names a colour the palette does not hold.
        */
       tagColor: (id: string): KeywordColor => {
-        const color = keywords.find((keyword) => keyword.id === id)?.color;
-        if (color && KEYWORD_PALETTE[color]) return KEYWORD_PALETTE[color];
-        return KEYWORD_PALETTE[suggestKeywordColor(id)] ?? KEYWORD_PALETTE[FALLBACK_KEYWORD_COLOR];
+        const stored = keywords.find((keyword) => keyword.id === id)?.color;
+        const suggested = suggestKeywordColor(id);
+        const color = stored && KEYWORD_PALETTE[stored]
+          ? stored
+          : KEYWORD_PALETTE[suggested] ? suggested : FALLBACK_KEYWORD_COLOR;
+        // Colour-blind-safe colours: the same tag, drawn in the palette
+        // colour nearest its own (lib/cvd-palette.ts). The stored colour stays.
+        if (colorBlindPalette) return CVD_CLASSES[cvdHue(color) ?? "grey"];
+        return KEYWORD_PALETTE[color];
       },
 
       /**
@@ -74,6 +82,6 @@ export function useKeywordFormat(scope?: TagScope | null) {
         );
       },
     }),
-    [keywords, nested],
+    [keywords, nested, colorBlindPalette],
   );
 }
diff --git a/lib/__tests__/cvd-palette.test.ts b/lib/__tests__/cvd-palette.test.ts
new file mode 100644
index 000000000..a026b9ce7
--- /dev/null
+++ b/lib/__tests__/cvd-palette.test.ts
@@ -0,0 +1,51 @@
+import { describe, it, expect } from 'vitest';
+import { CVD_COLORS, cvdColor, cvdHue } from '../cvd-palette';
+
+describe('cvdHue', () => {
+  it('maps the default calendar and tag colours onto separate palette colours', () => {
+    expect(cvdHue('#ef4444')).toBe('vermillion');
+    expect(cvdHue('#f97316')).toBe('orange');
+    expect(cvdHue('#eab308')).toBe('yellow');
+    expect(cvdHue('#22c55e')).toBe('bluishGreen');
+    expect(cvdHue('#06b6d4')).toBe('skyBlue');
+    expect(cvdHue('#3b82f6')).toBe('blue');
+    expect(cvdHue('#a855f7')).toBe('reddishPurple');
+  });
+
+  it('keeps red and green apart, the pair red-green colour blindness merges', () => {
+    expect(cvdHue('#dc2626')).not.toBe(cvdHue('#16a34a'));
+    expect(cvdHue('#b91c1c')).toBe('vermillion');
+    expect(cvdHue('#15803d')).toBe('bluishGreen');
+  });
+
+  it('reads tag palette names, with their light and dark shades', () => {
+    expect(cvdHue('red')).toBe('vermillion');
+    expect(cvdHue('teal-light')).toBe('skyBlue');
+    expect(cvdHue('indigo-dark')).toBe('blue');
+    expect(cvdHue('gray')).toBe('grey');
+  });
+
+  it('reads short hex, rgb() and hsl()', () => {
+    expect(cvdHue('#f00')).toBe('vermillion');
+    expect(cvdHue('rgb(0, 128, 0)')).toBe('bluishGreen');
+    expect(cvdHue('hsl(220, 80%, 50%)')).toBe('blue');
+  });
+
+  it('turns greys grey and gives up on what it cannot read', () => {
+    expect(cvdHue('#777777')).toBe('grey');
+    expect(cvdHue('var(--color-primary)')).toBeNull();
+    expect(cvdHue('')).toBeNull();
+    expect(cvdHue(undefined)).toBeNull();
+  });
+});
+
+describe('cvdColor', () => {
+  it('draws a colour as it is while the setting is off', () => {
+    expect(cvdColor('#3b82f6', false)).toBe('#3b82f6');
+  });
+
+  it('draws the palette colour while it is on, and leaves unreadable colours alone', () => {
+    expect(cvdColor('#3b82f6', true)).toBe(CVD_COLORS.blue);
+    expect(cvdColor('var(--color-primary)', true)).toBe('var(--color-primary)');
+  });
+});
diff --git a/lib/cvd-palette.ts b/lib/cvd-palette.ts
new file mode 100644
index 000000000..d2b2e7e7a
--- /dev/null
+++ b/lib/cvd-palette.ts
@@ -0,0 +1,129 @@
+/**
+ * The colour-blind-safe palette behind Settings > Accessibility >
+ * "Colour-blind-safe colours" (colorBlindPalette).
+ *
+ * Tags, folders and calendars keep the colours the user picked; this only
+ * changes how they are drawn. Every colour is moved to the nearest of the
+ * Okabe-Ito colours by hue: eight colours chosen to stay apart for
+ * protanopia, deuteranopia and tritanopia (Okabe & Ito, "Color Universal
+ * Design", 2008). Two picked colours of a similar hue (blue and indigo) can
+ * land on the same one; the names next to them still tell them apart.
+ */
+
+export const CVD_COLORS = {
+  vermillion: "#D55E00",
+  orange: "#E69F00",
+  yellow: "#F0E442",
+  bluishGreen: "#009E73",
+  skyBlue: "#56B4E9",
+  blue: "#0072B2",
+  reddishPurple: "#CC79A7",
+  grey: "#999999",
+} as const;
+
+export type CvdHue = keyof typeof CVD_COLORS;
+
+/** The hues of the tag palette (stores/settings-store KEYWORD_PALETTE), as Tailwind's 500 shades. */
+const PALETTE_HUES: Record<string, string> = {
+  red: "#ef4444",
+  orange: "#f97316",
+  amber: "#f59e0b",
+  yellow: "#eab308",
+  lime: "#84cc16",
+  green: "#22c55e",
+  teal: "#14b8a6",
+  cyan: "#06b6d4",
+  blue: "#3b82f6",
+  indigo: "#6366f1",
+  purple: "#a855f7",
+  pink: "#ec4899",
+  gray: "#6b7280",
+};
+
+/** Hue (0-360) and saturation (0-1) of a colour, or null when it can't be read. */
+function hueAndSaturation(color: string): { hue: number; saturation: number } | null {
+  let r: number, g: number, b: number;
+  const value = color.trim().toLowerCase();
+  const hex = /^#([0-9a-f]{3,8})$/.exec(value);
+  if (hex) {
+    let digits = hex[1];
+    if (digits.length === 3 || digits.length === 4) digits = digits.slice(0, 3).split("").map((d) => d + d).join("");
+    if (digits.length !== 6 && digits.length !== 8) return null;
+    r = parseInt(digits.slice(0, 2), 16);
+    g = parseInt(digits.slice(2, 4), 16);
+    b = parseInt(digits.slice(4, 6), 16);
+  } else {
+    const rgb = /^rgba?\(\s*([\d.]+)[\s,]+([\d.]+)[\s,]+([\d.]+)/.exec(value);
+    const hsl = /^hsla?\(\s*([\d.]+)(?:deg)?[\s,]+([\d.]+)%[\s,]+([\d.]+)%/.exec(value);
+    if (rgb) {
+      [r, g, b] = [Number(rgb[1]), Number(rgb[2]), Number(rgb[3])];
+    } else if (hsl) {
+      return { hue: Number(hsl[1]) % 360, saturation: Number(hsl[2]) / 100 };
+    } else {
+      return null;
+    }
+  }
+  const [rn, gn, bn] = [r / 255, g / 255, b / 255];
+  const max = Math.max(rn, gn, bn);
+  const min = Math.min(rn, gn, bn);
+  const delta = max - min;
+  const lightness = (max + min) / 2;
+  const saturation = delta === 0 ? 0 : delta / (1 - Math.abs(2 * lightness - 1));
+  let hue = 0;
+  if (delta !== 0) {
+    if (max === rn) hue = ((gn - bn) / delta) % 6;
+    else if (max === gn) hue = (bn - rn) / delta + 2;
+    else hue = (rn - gn) / delta + 4;
+    hue *= 60;
+    if (hue < 0) hue += 360;
+  }
+  return { hue, saturation };
+}
+
+/**
+ * The palette colour for `color`: a CSS colour (#hex, rgb(), hsl()) or a
+ * tag palette name ("red", "teal-light"). Null when it can't be read.
+ */
+export function cvdHue(color: string | null | undefined): CvdHue | null {
+  if (!color) return null;
+  const paletteName = color.replace(/-(light|dark)$/, "");
+  const parsed = hueAndSaturation(PALETTE_HUES[paletteName] ?? color);
+  if (!parsed) return null;
+  const { hue, saturation } = parsed;
+  if (saturation < 0.15) return "grey";
+  if (hue < 18 || hue >= 345) return "vermillion";
+  if (hue < 44) return "orange";
+  if (hue < 70) return "yellow";
+  if (hue < 165) return "bluishGreen";
+  if (hue < 200) return "skyBlue";
+  if (hue < 255) return "blue";
+  return "reddishPurple";
+}
+
+/**
+ * The colour to draw `color` in: itself, or its colour-blind-safe
+ * replacement when `enabled`. A colour it can't read is drawn as it is.
+ */
+export function cvdColor(color: string, enabled: boolean): string {
+  if (!enabled) return color;
+  const hue = cvdHue(color);
+  return hue ? CVD_COLORS[hue] : color;
+}
+
+/**
+ * Tailwind classes for each palette colour, written out so Tailwind
+ * generates them (it only finds classes that appear verbatim). Used where
+ * a colour is drawn through classes (tag lozenges, folder icons) instead of
+ * an inline style. Text stays in the text colour: several of these colours
+ * are too light to read as text.
+ */
+export const CVD_CLASSES: Record<CvdHue, { dot: string; icon: string; fill: string; border: string; text: string; rowTint: string }> = {
+  vermillion: { dot: "bg-[#D55E00]", icon: "text-[#D55E00]", fill: "bg-[#D55E00]/15", border: "border-[#D55E00]", text: "text-foreground", rowTint: "bg-[#D55E00]/10" },
+  orange: { dot: "bg-[#E69F00]", icon: "text-[#E69F00]", fill: "bg-[#E69F00]/15", border: "border-[#E69F00]", text: "text-foreground", rowTint: "bg-[#E69F00]/10" },
+  yellow: { dot: "bg-[#F0E442]", icon: "text-[#F0E442]", fill: "bg-[#F0E442]/20", border: "border-[#F0E442]", text: "text-foreground", rowTint: "bg-[#F0E442]/15" },
+  bluishGreen: { dot: "bg-[#009E73]", icon: "text-[#009E73]", fill: "bg-[#009E73]/15", border: "border-[#009E73]", text: "text-foreground", rowTint: "bg-[#009E73]/10" },
+  skyBlue: { dot: "bg-[#56B4E9]", icon: "text-[#56B4E9]", fill: "bg-[#56B4E9]/15", border: "border-[#56B4E9]", text: "text-foreground", rowTint: "bg-[#56B4E9]/10" },
+  blue: { dot: "bg-[#0072B2]", icon: "text-[#0072B2]", fill: "bg-[#0072B2]/15", border: "border-[#0072B2]", text: "text-foreground", rowTint: "bg-[#0072B2]/10" },
+  reddishPurple: { dot: "bg-[#CC79A7]", icon: "text-[#CC79A7]", fill: "bg-[#CC79A7]/15", border: "border-[#CC79A7]", text: "text-foreground", rowTint: "bg-[#CC79A7]/10" },
+  grey: { dot: "bg-[#999999]", icon: "text-[#999999]", fill: "bg-[#999999]/15", border: "border-[#999999]", text: "text-foreground", rowTint: "bg-[#999999]/10" },
+};