diff --git a/src/calendar-app/calendar/gui/CalendarGuiUtils.ts b/src/calendar-app/calendar/gui/CalendarGuiUtils.ts
index a1ac366f5359..795caf8a0a03 100644
--- a/src/calendar-app/calendar/gui/CalendarGuiUtils.ts
+++ b/src/calendar-app/calendar/gui/CalendarGuiUtils.ts
@@ -70,7 +70,7 @@ import { CalendarEventTimes, CalendarViewType, cleanMailAddress, isAllDayEvent }
 import { CalendarEvent, UserSettingsGroupRoot } from "../../../common/api/entities/tutanota/TypeRefs.js"
 import { ProgrammingError } from "../../../common/api/common/error/ProgrammingError.js"
 import { size } from "../../../common/gui/size.js"
-import { isValidColorCode } from "../../../common/gui/base/Color.js"
+import { hslToHex, isColorLight, isValidColorCode, MAX_HUE_ANGLE } from "../../../common/gui/base/Color.js"
 import { GroupColors } from "../view/CalendarView.js"
 import { CalendarInfo } from "../model/CalendarModel.js"
 import { EventType } from "./eventeditor-model/CalendarEventModel.js"
@@ -82,6 +82,8 @@ import { UserController } from "../../../common/api/main/UserController.js"
 import { ClientOnlyCalendarsInfo } from "../../../common/misc/DeviceConfig.js"
 import { SelectOption } from "../../../common/gui/base/Select.js"
 import { RadioGroupOption } from "../../../common/gui/base/RadioGroup.js"
+import { ColorPickerModel } from "../../../common/gui/base/colorPicker/ColorPickerModel.js"
+import { theme } from "../../../common/gui/theme.js"
 
 export interface IntervalOption {
 	value: number
@@ -972,8 +974,9 @@ export function getDisplayEventTitle(title: string): string {
 
 export type ColorString = string
 
-export function generateRandomColor(withHashtag: boolean = false): ColorString {
-	return (withHashtag ? "#" : "") + Math.random().toString(16).slice(-6)
+export function generateRandomColor(): ColorString {
+	const model = new ColorPickerModel(!isColorLight(theme.content_bg))
+	return hslToHex(model.getColor(Math.floor(Math.random() * MAX_HUE_ANGLE), 2))
 }
 
 export function renderCalendarColor(selectedCalendar: CalendarInfo | null, groupColors: Map<Id, string>) {
diff --git a/src/calendar-app/calendar/gui/EditCalendarDialog.ts b/src/calendar-app/calendar/gui/EditCalendarDialog.ts
index d9249b181768..e88a93c4d15f 100644
--- a/src/calendar-app/calendar/gui/EditCalendarDialog.ts
+++ b/src/calendar-app/calendar/gui/EditCalendarDialog.ts
@@ -14,6 +14,7 @@ import type { CalendarModel } from "../model/CalendarModel.js"
 import { DEFAULT_ERROR } from "../../../common/api/common/TutanotaConstants.js"
 import { LoginButton } from "../../../common/gui/base/buttons/LoginButton.js"
 import { ColorPickerView } from "../../../common/gui/base/colorPicker/ColorPickerView"
+import { generateRandomColor } from "./CalendarGuiUtils.js"
 
 export type CalendarProperties = {
 	name: string
@@ -125,7 +126,11 @@ export function showCreateEditCalendarDialog({
 	isNewCalendar = true,
 	calendarModel,
 }: CreateEditDialogAttrs) {
-	if (color !== "") color = "#" + color
+	if (color !== "") {
+		color = "#" + color
+	} else if (isNewCalendar && isExternalCalendarType(calendarType)) {
+		color = generateRandomColor()
+	}
 
 	const nameStream = stream(name)
 	const colorStream = stream(color)
diff --git a/src/calendar-app/calendar/view/CalendarView.ts b/src/calendar-app/calendar/view/CalendarView.ts
index b39dc75601bc..cb97ede91181 100644
--- a/src/calendar-app/calendar/view/CalendarView.ts
+++ b/src/calendar-app/calendar/view/CalendarView.ts
@@ -63,7 +63,14 @@ import { GroupInvitationFolderRow } from "../../../common/sharing/view/GroupInvi
 import { SidebarSection } from "../../../common/gui/SidebarSection"
 import type { HtmlSanitizer } from "../../../common/misc/HtmlSanitizer"
 import { ProgrammingError } from "../../../common/api/common/error/ProgrammingError"
-import { calendarNavConfiguration, calendarWeek, daysHaveEvents, shouldDefaultToAmPmTimeFormat, showDeletePopup } from "../gui/CalendarGuiUtils.js"
+import {
+	calendarNavConfiguration,
+	calendarWeek,
+	daysHaveEvents,
+	generateRandomColor,
+	shouldDefaultToAmPmTimeFormat,
+	showDeletePopup,
+} from "../gui/CalendarGuiUtils.js"
 import { CalendarEventBubbleKeyDownHandler, CalendarPreviewModels, CalendarViewModel, MouseOrPointerEvent } from "./CalendarViewModel"
 import { CalendarEventPopup } from "../gui/eventpopup/CalendarEventPopup.js"
 import { showProgressDialog } from "../../../common/gui/dialogs/ProgressDialog"