Raw vs Cooked Egg Yolk Color

Question

Why do egg yolks change color from orange or dark yellow to yellow or light yellow when cooked, esp. hard boiled?

Answer 1

This is due to the proteins in the yolk denaturing and aggregating - basically the same reason the white (albumen) turns white from clear.

Think about the color that would result if you mixed a dark yellow color with some of the color white (i.e. I'm not talking about mixing yolk with albumen here, just colors) - it would lighten to make a lighter yellow