It's interesting. I buy into the blue upper surfaces, based on what Bell has to say and the photo documentation.
What I see as wrong here is the wings would have been blue first. That was the whole point of this, cover the silver since N.A. was now supplying them in natural metal with silver painted wings. before we (the USAAF) decided it was unnecessary. So this should be reversed. Blue on the outer wings, with green. (or more blue) over the invasion bars.
Not trying to poop on this guys work. I like it, I just don't think it fits the facts. As I understand them.