A few years back I briefly thought that a rich yolk color was a quality signal, until I found that additives could produce that color cheaply. The color comes f

A few years back I briefly thought that a rich yolk color was a quality signal, until I found that additives could produce that color cheaply. The color comes from dietary carotenoids [1]. Companies like BASF sell carotenoid feed additives that producers can employ to get a yolk color as rich as desired: https://nutrition.basf.com/global/en/animal-nutrition/our-products/carotenoids https://nutrition.basf.com/global/en/animal-nutrition/our-pr... [1] https://en.wikipedia.org/wiki/Carotenoid https://en.wikipedia.org/wiki/Carotenoid