SkinStudio is a WindowBlinds skin-creation tool that lets you customize the Windows 98/ME/NT/2000/XP user interface with skins that you design and create. Version 2.5 allows users to change the colors of their visual styles along with having a host of new tools for making it easier to create visual styles from a mock up.
More info:
hxxp://www.stardock.com/products/skinstudio/