There are a lot of factors that can influence the egg yolk color a hen produces, and most of it comes down to diet, says Sunoh Che, DVM, PhD
The composition of the hen’s feed: The amount of yellow-orange carotenoids [plant pigments], like lutein from alfalfa meal and zeaxanthin from marigold flower
The amount of corn in the feed: Corn can influence how yellow a yolk is, says Blatchford.
That’s why most of our grocery store eggs are a yellow color, but not really bright.
Xanthophyll content: Xanthophyll is a yellow compound that influences egg yolk color, says Hillary Ayers, family and consumer sciences agent
Access to a fresh pasture: “Hens with access to fresh grass and pasture tend to produce eggs with more vibrant yolk colors,” says Che