There is the following issue with Silverlight: having reference to a Style does not help obtaining the values for say Foreground or Fill, or any other property, since the Property objects (set to Setter.Property) are translated to native resources and there is no way of obtaining any useful information out of those.
We are currently extending the styling mechanism of the RadChart to enable easy color customization, i.e. Styles will be built using data provided by the developer. That, however, will only allow you to provide custom colors, but not get them back since the fore-mentioned problem will still persist.
the Telerik team