I haven't really noticed drastic color differences in the ones i've seen, but it is entirely possible. I suspect that that red color is just a trait of youth that eventually turns to brown in adults. That being said, there are now several different species of Theloderma in the U.S. Just recently there were imports of T. bicolor, which looks very similar to corticale, and T. asperum, which is a little more unique looking.

Alex