Even though all property settings are available through the StyleSheet object, it would be really hard to process the complex structure and find the needed property values.
The main issue comes form the fact that themes define property values for various states of different elements. For example, GridViewCell elements have different appearance depending on the value of IsCurrent and IsSelected properties.
There is also property-value inheritance mechanism, similar to Control's ambient properties. This means an element may have a different background color depending on its parent's style. Another problem is that the appearance of an element is formed by a number of properties which should be respected in order to have correct results.
If you need information about the runtime appearance properties (unlike the toolbox toolstrip for example), elements of RadControls, use the actual property values for painting. That's why, the simpler solution would be to check the values of different properties of RadGridView at runtime, similar to the approach of RadControlSpy.
Another solution is to simulate grid elements and use style API to apply style over these template objects - grid cells and rows, which can be used to check the resulting property values. We have prepared an application that demonstrates this approach.
Please, if you have any questions, do not hesitate to write.