Hi, yes, we have this feature in our wishlist since some time ago. We'll check what can be done, but unfortunately it involves several technical issues:
1) Forest Color uses large data structures which are stored in Forest, as the hierarchy of elements in the mesh (these are created for each tree model).
Since the GPU cannot access directly to the Forest memory, we should provide to ChaosGroup some way to copy all these data to the GPU RAM.
2) The binary code of Forest Color cannot run in GPU (it's compiled for CPU), and we cannot write a GPU shader because V-Ray RT doesn't allow that (there is not a SDK). So, we should simplify the source code (it's a bit complex) and give to it ChaosGroup so they compile and integrate it within of V-Ray. This is a complex and completely new workflow for us.
I'm sorry by the technical terms, by i wanted to provide a detailed explanation of why this feature has not been implemented yet.