Switch all of McCoy's "Green blooded son of a bitch!" stuff to "Dark-skinned son of a bitch!" and his attitude really gets disgusting.
Right on. Not only McCoy, but others kidded Spock about his blood, ears, and so on. And it only worked because it's all make-believe.
Imagine a scene with McCoy and Sulu, and you hear the doctor, "Why you yellow-skinned, slant-eyed..."