Outlook doesn't have import/export Master Category feature so you can easily share custom categories with others, other than by exporting the registry and overwriting the registry entry on the other computers. However, it's not necessary to export the master category list and import it on everyone's computer, any category used on an Outlook item but not on the master category list is marked with "(not on master list)". These categories can be searched or filtered on, they just aren't listed in the master list.
The only time using a standardized Master Category list makes sense is if your company uses a lot of custom categories. When the categories are on the master list it's easier for the users to select the right category to their items, although it’s even easier to use a custom form that lists the categories users should choose from. For more information on using the Master Category list, see Outlook Categories and Color Categories
Published April 26, 2004. Last updated on April 25, 2013.