I don't know the site, but you could use a program called RC mod to change the color of the top and bottom bars manually.
The type of file you’re talking about btw is called .tsk
Otherwise you might just want to download a free theme generator... here’s a link and .cab to point you in the right direction.
The link is to article about a free theme generator and a detailed tutorial on how to use it, and the .cab is for RC Mod version 2.1.
http://forum.ppcgeeks.com/showthread.php?t=22087