How can I create a new category in Office 365 calendar using the REST API?

Question

The application I am currently working on adds new events in the user's Office 365 calendar. I would like to display the events in different colors based on some criteria. I think I can achieve that using categories but I didn't find a way to add a new category or at least get a list of the available categories in the user's calendar.
I read the documentation available here but it doesn't say anything related to categories.

Answer 1

We added category support in the beta version of the Microsoft Graph API.

Announcement: https://blogs.msdn.microsoft.com/exchangedev/2017/10/09/new-outlook-apis-in-the-microsoft-graph-rooms-rules-categories-headers-and-time-zones/

Beta reference: https://developer.microsoft.com/en-us/graph/docs/api-reference/beta/api/outlookuser_post_mastercategories

Example:

POST https://graph.microsoft.com/beta/me/outlook/masterCategories
Content-type: application/json
Content-Length: 70

{
      "displayName":"Project expenses",
      "color":"preset9"
}

You can do similar operations using the Outlook REST API using a URL like:

https://outlook.office.com/api/beta/me/mastercategories

There's also a new permission scope that you need for this. For Graph, it's MailboxSettings.ReadWrite (https://outlook.office.com/MailboxSettings.ReadWrite for the Outlook API).