Color categories are a great way to visually group similar messages, tasks, contacts, or calendar events.
Each category has a generic name, such as Red Category and Blue Category. The first time that you assign a color category to an item, you are prompted to rename the color category. This is your opportunity to choose a category name that is meaningful to you. If don’t set a custom name, don’t worry. You can change the name at any time.
In any view, click Home.
In the Tags group, click Categorize, and then click All Categories.
Note: For calendar items, the Tags group appears on the Appointment or Meeting tab. For an open contact or task, the Tags group appears on the Contact or Task tab.
Click a category, and then click Rename.
Type the new name for the color category, and then press Enter.