Can spray tan stain plastics?

Question: Is it possible for spray tans to stain the plastic white keys on a piano? We're working on some piano keys that we think this may be the "culprit".

You know, spray tans for the wedding party (including the pianist maybe) who got nervous/sweaty playing, the spray wasn't "set" yet hence the color transferred to the keys used most in the middle of the piano.

We're getting it off....but with a lot of elbow grease and a specialized cleaner! Had we not found something that works, we'd have to replace the keys....a big and expensive job!

Answer: You know, I have absolutely no idea. You are the very first person that has ever brought this up.
Lets see - spray tan does stain nails if they have no nail polish on them, so if the keys would be porous, that possibly could happen I imagine. But by the same token if somebody was a heavy smoker and had tobacco stained fingers, it could also happen?
I think that there could be few different reasons for it, so lets just be grateful that you found something that can get it off, eh?