For the notes, Monsters probably do bleed, although of course it's not blood. Reason we don't see it most of the time is because black-and-white. Instead of blood, it's probably a liquid form of magic. Couple be green, could be blue, but everyone draws red because it's simple and we all know it.

'course this goes for all 'living' monsters. Undead monsters like Skeletons or Ghosts probably just start crumbling to dust then and there.