One might try some of the threads in the custom sounds and skins sub-forum. There are some tutorials (I have one, by no means the only one, but maybe a good place to start -- see link in signature) and there are some helpful threads, as well as some HTC references on the main webpage (such as this:
http://www.hitechcreations.com/ahhelp/skins.html).
Please keep in mind that you can't just randomly color a skin. HTC accepts historical skins that saw combat (i.e. not state-side trainer skins, not captured country skins, not unarmed recon skins), but if you are interested I would say there are a number of folks willing to help a beginner in the skins forum.
