Manipulating Tree Builder Tree Colors

Hey folks, this is a tougher question, and I wasn't even sure which forum to put it in since it potentially crosses many topics. I need to be able to, based on user state, swap between fully-rendered trees, and silhouettes of trees. It works with SpeedTree trees, but doesn't with the Tree Builder trees (and the trees I have for my environment are, of course, done in Tree builder).

I tried mucking about with the internals of the Tree builder optimized shaders and such, and screwed up my project so bad I had to revert to a backup.

Here it is working in SpeedTree. Any thoughts as to how this effect could be accomplished with tree builder trees?