[funkymonkey]

To change the product category block open the skin1_customer.css template and edit the hex codes for the VertMenuCatTitle and VertMenuCatWelcBoxNewsTitle (down toward the bottom of the file.) As you will see, there are several component changes needed to make everything blend nicely. I haven't yet found the code for the subcategory colours - I suspect it's in the same template though. I printed the template (ten pages) and highlighted all the hex codes, labelling them as they're identified. X-Cart quoted me $100 for a custom colour theme but I think it's best in the long run to know where everything is located.
Good luck!