I have a slate merle border collie. (And no, I didn't go looking for one, he was a rescue ) His nose leather is blueish/purple and where a normal merle would have black spots, his are gray/dark gray. He does have all the hair on his ears, unlike that other dog on that website. He has been described as a slate merle and a slate blue merle so I really don't think there is a difference between the two.