Chickens and other poultry naturally produce eggs with pale yellow to orange yolks, largely depending on their diet. You can change the color of an egg yolk by changing what the chicken eats or by injecting a fat-soluble dye into an egg yolk.
Egg Color and Nutrition
Eggshell and yolk color are unrelated to the nutritional content or flavor of an egg. The shell color naturally ranges from white to brown depending on the breed of chicken. Yolk color depends on the diet fed to the hens. The shell thickness, cooking quality, and value of an egg is not affected by its color.
Can I Dye Egg Yolks?
The short answer is yes, you can dye them. However, because egg yolks contain lipids, you need to use a fat-soluble dye. Ordinary food colors can be used to change egg white color, but won't spread throughout an egg yolk. You can find oil-based food dyes at Amazon and at cooking stores. Simply inject the dye into the yolk and allow time for the color to permeate the yolk.
Changing Yolk Color at the Source
If you raise chickens, you can change the color of the yolks of the eggs they produce by controlling their diet. Specifically, you control the carotenoids or xanthophylls they eat. Carotenoids are pigment molecules found in plants, responsible for the orange of carrots, red of beets, yellow of marigolds, purple of cabbages, etc. Certain commercial pigments are available as supplements added to feed to influence egg yolk colors, such as BASF's Lucantin(R) red and Lucantin(R) yellow. Natural foods also affect yolk color. Yellow, orange, red, and possibly purple may be obtained, but for blue and green you likely have to resort to synthetic dyes.
|nearly colorless||white cornmeal|
|pale yolks||wheat, barley|
|medium yellow yolks||yellow cornmeal, alfalfa meal|
|deep yellow yolks||marigold petals, kale, greens|
|orange to red yolks||carrots, tomatoes, red peppers|
Hard Boiled Green Egg Yolks
You can get grayish green egg yolks by hard boiling eggs. The discoloration results from a harmless chemical reaction in which hydrogen sulfide produced by sulfur and hydrogen in the egg whites reacts with iron in the yolks. Few people consider this an attractive food color, so you may wish to prevent this reaction by immediately chilling eggs with cold water after hard boiling them.