It is of course canonical to paint certain demons in certain ways. Nothing wrong with that.
Green and brown to represent bile and decay--the corrupted flesh. Occasionally a startling, bowel-y purple, as a reminder that what's inside is a mystery, and mysteries can be rubbery.
But there are other possible associations. This sculpt in particular, with its nicks and gouges, makes me think of a cut finger that has been under a bandage for a long time. The flesh is soft and overly pale. The wound is a bloodless red with an alien topography to the under-surface that is normally hidden beneath the skin.
This association makes me reflect that beneath the surface of things, death is a powerful and pervasive motivating force. It's inside everything, even if we don't recognize it.
That is one of the metaphorical faces of Chaos--the animating force of death is portrayed literally, incorporated in the body of the demon and alluded to in the gong of skulls on which the march is beaten.
I have painted this guy to reflect this idea. I call him The Bloat.