You can apply a custom theme to any of the controls. For more information you can follow the link below:
If you have further questions please do not hesitate to ask us.
I hope this will help you.
P.S: If you want to reduce the size of your Silverlight application, you should check our latest Silverlight tool online - Assembly Minifier (http://blogs.telerik.com/blogs/posts/10-06-10/telerik_assembly_minifier.aspx
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