Why do dead bodies turn yellow?

Well there are more variables in this question than you might realize, it would depend on what he died from, like liver failure or disease can make you turn yellow or jaundice, most people get pale kind of grayish white, if you die from lack of oxygen you tend to turn blue first. If you are black in skin color you usually tend to look pretty gray, if you are Asian or Hispanic kinda yellowish pale so it all depends on the color your skin was before you die and what the cause of death is.