Green Fondant Elephant - color change?

So, my fondant elephant is still on the window sill watching the snow (yes, it is snowing again and, yes, I did forget about the elephant and left it where I was photographing it!) and it changed color!  It's green!
  You can see the original gray color underneath.   As I've said before, this is new to me, but I didn't know that fondant would change colors like that! I'm having fun learning and glad this wasn't going on a cake, but no one mentioned much about storing finished fondant pieces.  Has this ever happened to you?  Is it exposure to air or light?