How do I share categories in an shared calendar

Categories and category colors are not shared across users in a shared Outlook calendar. Each mailbox uses its own category list, so other people will see and use their own categories and colors rather than a single shared set.

What is possible:

• People can apply categories to items in a shared calendar if they have the required permissions.
• In Outlook on the web/new Outlook, when granting delegate access, the calendar owner can enable Let delegate manage categories.
• In shared calendar scenarios, permissions such as Editor, Owner, or Delegate affect whether someone can apply, create, or manage categories, but they do not make category colors identical for everyone.

Important limitation:

• Even if someone has Owner access to the shared calendar, category colors still do not automatically sync to other users.
• Only the mailbox owner can rename a category in the shared folder’s Color Categories list.

If the goal is for everyone to see the same visual labeling, that is not supported through shared Outlook categories and colors.

• Shared Outlook Calender category colors won't show on others' calender - Microsoft Q&A
• You cannot change a user's categories when you work as a delegate in Outlook
• New Outlook tips for executive admins and delegates