This article is relevant for people who conduct demos or training on Outlook. During demos we create custom color Outlook categories. These categories remain customized for the next demo as well. Ideally I would want the categories to have default names (Red Category, Blue Category and so on). How to clean all of them quickly just before the demo? Simple.
Start Outlook with the Startup Switch /clearcategories
<office installation path>outlook.exe /clearcategories.
This DOES NOT remove custom categories which have already been applied to Outlook items like mails, appointments or tasks. These have to be removed separately. But it does remove the custom descriptions. Now the category dialog looks like this.