Media Center Themer is an addin for Windows Media Center than enables you to customize lots of the look and feel of Media Center and it does it without modifing the actual Media Center Code. Verion 1.3 was released yesterday and adds auto-colorize
Among the updates, a new Auto-Colorize feature has been added to greatly simplify the creation of themes using all sorts of colors other than the default blue. With the new “Colorize” XML attribute, the software now automatically changes the color of more than 300 Media Center pictures (buttons, overlays, …), allowing you to concentrate on more important stuff.
You can get the update from the developers site