At this point we don't have such resource, but will definitely consider creating one for the future. Your Telerik points are updated in appreciation of the feedback.
In the meantime, the only thing I could suggest is to check the Silverlight demo for RadSpreadsheet
. The model of the RadSpreadProcessing library is also used with the UI control for Silverlight, so the demo will allow you to see a preview of the predefined font and color schemes, as well as a set of combinations between the two. To switch between the themes go to the Themes group in the Page Layout tab of the ribbon: http://screencast.com/t/DIv9jTf6oQ
I hope this is useful.