In your Mac's menu bar, click Outlook. Then, choose Preferences. Click Categories. Use the plus and minus buttons to add and remove categories.

Microsoft Outlook for Mac allows you to categorize email messages, events, contacts, and other items using colors. Categories are color-coded to help you quickly identify which items belongs to which category. You can add a new category, edit an existing category, or delete them as you like. Microsoft allows you to change the color or name of a category.

1) In your Mac's menu bar, click Outlook and choose Preferences.

2) Click Categories.

3) You can edit existing categories by double-clicking on the corresponding field you would like to change. To add a new category, click the plus symbol (+).

Give the category a name and assign it a color. Then, click Create.

To remove a category, click the minus symbol (−).

Confirm removal by clicking Delete.

Outcome

You have successfully edited your categories. These will stay in sync across your Microsoft 365 account to your various devices.