I believe Trampas stated in his spotlight interview that it is one of the more complicated finishes, because it is indeed a multi-stain&sand process. Just look at what he did for Shawn's cut-off pieces for his Employee Guitar - two different stains with careful sanding in between. And those were relatively easy finishes!
My guess would be a light gray stain, sand, red, sand a bit heavier, blue, light sand, green. But I also bet PRS has a trademark on the process, or at least classifies it as their IP.