Change a calendar name or color on iCloud.com
You can assign a different color to each calendar you create so you can easily tell which calendar an event belongs to.
You can edit a calendar’s name and color at any time. When you change a calendar’s color, all of its events change to the new color.
In Calendar on iCloud.com, click Edit at the bottom of the sidebar.
Do any of the following:
Change a calendar’s name: Click the calendar’s name and edit it.
Change a calendar’s color: Click the Color button next to the calendar’s name, then choose a color.
Click Done at the bottom of the sidebar.
Note: Changes you make appear on every device that has iCloud Calendar turned on. You can’t change the name or color of the Birthdays calendar. Color changes aren’t visible in Microsoft Outlook.