My baby bun also has yellowish feet. I am guessing it is because of the hay in his litter box, he likes to sit in there. The breeder I got him from said that it fades when they shed? But they aren't damp or anything. I agree with the above posts, I would say unless they are damp constantly. His feet used to be really yellow when I first got him because they put vitamins in his water bowl that turned the water yellow and he liked to play in his water! lol I can say that in 3 weeks it has faded significantly.