User blog comment:Kogath/Monster Hunter XX Discussion/@comment-26532315-20161027164501/@comment-26261665-20161027201735

^ I don't think anything on the lore suggested the hypotetical Red Diablos fighting King Diablos. At least not at BannedLagiacrus' blog.

@Raptorhunter6 Don't know about 3U since I haven't played it for ages, but in 4U normal Diablos also have a bit of green tint if I recall correctly. Your idea about mid-way Black Diablos in interesting, but since it is called a King and it has what looks like an extra horn, I think it's something different...