See if this helps: http://www.slipstick.com/outlook/olcat.htm

Might we also offer another possible suggestion.  Outlook 2007 has a feature
that will allow you to very easily upgrade your color categories from any
other .PST file you open in your folder list.  Once you open the .PST file
(File > Open > Outlook Data File), it will appear in your folder list in the
left pane of Outlook 2007.  At this point, simply right-click the newly
opened folder and choose the Properties > General Tab > Upgrade to Color
Categories button.  This will add all the color categories in that data file
to your current Outlook.  Once you have added the color categories I assume
you could simply remove the data file folder from the list and the data file
from the hard drive if needed.  If you are upgrading multiple computers, you
might be able to simply plug in a flash/thumb drive at the workstation,
upgrade the colors, delete the data folder in Outlook, and then simply move
the flash/thumb drive to the next workstation to be upgraded.  Good luck!