VisualStyleBuilder is still in beta, but the most important is that this is a complicated application and some of it`s features dos not work the best way in all possible browsers. In my opinion if you want to take all of the advantages of the tool, you should find a way to use it with FireFox.
VisualStyleBuilder has a simple navigation and options: Under colorize tab you could change the main colors/gradients in the sprite images. You have an option to use wen friendly colors with the web palette ColorPicker or RGB/HSV under HSV tab, and under Shift Colors tab you could change Hue/Saturation.
Under the other main tab - Fine Tune - you could change skin specific CSS options such as font-size properties, text color, background color, etc.
It is really simple and the video tutorials gives all the information that you need in order to operate with the tool.
This a video showing a simple colorization and font weight change in a RadButton: http://screencast.com/t/yhyd0jhMy
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