What causes the color of the yolk in hen's eggs?

The color of the yolk in hen's eggs primarily results from specific pigments known as xanthophylls, which are a type of carotenoid. These pigments are commonly found in the diet of hens. When hens consume feed that contains natural sources of these pigments, particularly yellow and green plants such as grasses, the xanthophylls get deposited in the egg yolk, resulting in its characteristic color.

While carotenoids are indeed present in feed and contribute to yolk color, the key pigments responsible for the yellow color specifically in yolks are often categorized as xanthophylls, making this choice particularly relevant. The genetic makeup of the hen does play a role in the overall health and productivity of the bird, but it is the diet that primarily determines the color of the yolk. Sunlight exposure can affect a hen's overall health and vitamin D levels, but it does not directly influence yolk color as the hen's diet does.