Also, for those wondering what the muddy patches look like clean - They're still brown spots. Basically the brown spots are special, coarse fur that clings to mud. And unlike most canines, Mongrooze(yeah I'm sticking with that one) actually has sweat glands, which serve mainly to keep the mud on it damp, so it never dries and hardens.
Unfortunately Mongrooze stinks really badly as a result. This all basically serves to keep it comfortable, since it likes to feel coated in mud, while spots like its flowery pink tail can stay exposed for reasons like
>>33623412 said. I think this anon's idea, but keeping the head, back, and tail mud, as well as the tail vines, would be perfect. I can take or leave the leaf ears, they make the Pokémon look more "Grass", but removing them also lessens the overlap with Leafeon.