When I customize a default Oulook 2010 color category on my Exchange server personal mailbox, giving it a more meaningful name, the next time I start Outlook it is reset to the default description again.
For example, the default Outlook 2010 color category lables are: Blue, Green, Orange, Purple, Red. Now, if I change the blue category label from "Blue" to "Documentation," it remains that way only through my current Outlook session. The next time I startup Outlook (when I come into work next) I find it has been reset from "Documentation" to "Blue" again. Outlook will not retain my custom labels on my personal mailbox.
Dave Englund