The link above is dead, unfortunately. Some foods have colors assigned to them, and if you feed enough of them your pet will change colors. I started stuffing brown foods in to my Allucia last night and she flipped over to brown earlier today. There's another forum of guides, and there's a food color chart in it. So far to me it seems like a bit of it is half common sense and half surprise, as foods you think will have a color assigned to them half of the time don't. Is there a certain color you want? I'm working on pink, black, and white right now on top of the brown I finished so I might be able to help a little bit with those colors at the very least.