It makes sense to me. The way I think of it is if you have two translucent sheets of paper. One of the papers is yellow and the other is blue. If you over lap those papers, you see green. The paper really isn't green at all, but it appears to be anyway. I'm not sure if that's really how it works, but that is the way I see. You can def. have a green crested gecko apparently, but it's not really a pigment that they have. It's a combination of two pigments put together. Someone correct me if I'm wrong, lol!