OK, done this now...you will need to press F5 (or perhaps even CTRL + F5) in order to observe the changes.
I've only accounted for Administrators and Moderators since I had a hard enough time coming up with just two different yet inoffensive colours, letalone four (colour is not my forté
). Even now, the red administrator colour doesn't really work in the Dark Red style. If anyone artsy happens to have any ideas in this regard, they would be very welcome.