Birds, fish, reptiles, amphibians, insects? Sure. But no mammals.
So I had to google it. Apparently, there is a sloth that moves around so slowly moss grows all over it and it doesn't care. So it may appear green, but only in the sense that it wears it.
This may have already been covered but whilst there might not be mammals that appear green to human eyes there are certainly mamals that appear green to the prey/predators in their environment.
Perfect example is a tiger who (to us) stands out like a sore thumb with its orange fur but is perceived as green with black stripes through the eyes of its prey, making it very well camouflaged in the jungle.