An orange egg yolk means that the hen was fed a diet high in beta-carotene, which is why the yolk is orange. The color of an egg yolk is determined by the hen's diet. A diet high in green vegetables will produce darker yolks, while a diet with mostly yellow and orange foods will result in eggs with lighter yolks. Foods that are rich in green vegetables give eggs with naturally darker yolks. This includes items like spinach, broccoli, and kale.