Have you ever noticed the color similarities with the King Penguin and King Eider? Any of those colors have anything to do with the "King" in both their names?
Really? You expected a serious answer to something that is likely not something anyone could know? Common names aren't like the scientific names that sometimes have an explanation connected to them. King Eider Somateria spectabilis and King Penguin Aptenodytes patagonicus, those names don't have any similarity I can see.
Both birds are mostly black and white because they are pelagic, many ocean going birds and mammals are B&W. It's actually pretty good camo on the water. Who knows what the original people who called them Kings were thinking. I suppose some comes from the color but with the penguin I'm sure some is from the size. There is a bigger penguin called the emperor, must be better then being king.