Microsoft Outlook provides color categories to help you organize related items. By default, the categories have generic names, such as Red Category and Blue Category. Each category can be renamed.
Note: The first time you assign a color category to an item, you are prompted to rename the color category.
In any view, on the Home tab, 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, respectively.
Click a category, and then click Rename.
Type the new name for the color category, and then press ENTER.