Outlook 2013 users can organize their emails conversation under different categories. The Categorize toolbar is under Tags section of the Home menu.
Users can also create custom categories and add it part of the regular once. Listed below are steps to create custom color categories in Outlook 2013.
Step 1: Click the Categorise option and select All Categories in the drop down list.
Step 2: Click New button under Color Categories
Step 3: Enter name for your custom categories and choose appropriate colour using the Color dropdown.
Step 4: Either you can set a Shortcut Key for the category or choose None.
Step 5: Then click OK button to confirm and save your changes.
Now the newly added category would be available in Categorize toolbar’s dropdown list.
And if you are going to use this category frequently then you can assign to Set Quick Click option. This would allow users to categorize email conversation by single clicking on the category column.