Egg color in general---and chicken egg color in particular---is often a mystery, even to people who have kept chickens for years. Where does the egg color come from? Is egg color related to ear lobe color? Does egg color have any effect on nutrition? Let's take a look at some of the more interesting myths about egg color here.
1. MYTH: Blue eggs are more nutritious than white or brown eggs.
False. Blue eggs are not inherently more nutritious than white or brown eggs by virtue of their color. Egg color doesn't affect the nutrition of the egg. The only thing that affects the nutrition of an egg is the hen's diet. Eggs laid by hens raised on pasture have less fat and cholesterol, and more healthy vitamin A, vitamin E, beta carotene and omega-3s. Note that commercial "free range" hens almost never have access to pasture. That myth might have its basis in the fact that blue egg layers are seldom used in commercial egg farms, so when you have a blue egg, it's likely to be more nutritious than what you get at the grocery store, because the hens are more likely to be raised in a small flock with access to pasture. However the nutrition is due to the way the birds are raised, not the egg color. Egg nutrition just doesn't have anything to do with the color of the shell.
2. MYTH: The color of a hen's eggs is determined by the color of her earlobes.
False. Egg color is not determined by ear lobe color. That myth has its basis in the fact that egg color frequently correlates with ear lobe color, even though it is not caused by ear lobe color. Breeds with white earlobes usually lay white eggs... except for Penedesencas and Empordanesas, which have white earlobes and lay dark chocolate colored eggs. Chickens with red earlobes usually lay eggs in shades of brown... except for Easter Eggers, Ameraucanas and Araucanas, which lay blue eggs (blue OR green in the case of Easter Eggers). Then there is the Silkie, which lays light brown or nearly white eggs; silkie earlobes are blue.
3. MYTH: Blue egg color means your chicken has a virus
False. Blue egg color is caused by the genetics of your chicken, not because your chicken is sick. We presume the basis of this myth is that someone just wanted a sensational headline. It's a misreading of a headline that's been making the rounds recently. If you read the article, you see they affirm that blue egg color is indeed caused by genetics: "A new study found that a single gene, called callee oocyan, is responsible for the odd coloration of these blue chicken eggs." It's just that studies have shown that scientists believe the mutation was originally caused by a virus. In truth, brown and blue eggs do differ in more than just shell color. Brown egg color is laid on the outside of the shell, while blue color actually goes all the way through the shell, even to the inside of the shell. Originally, it was thought that color pigments were synthesized in the blood by the breakdown of hemoglobin, but research shows it is more likely that they are actually synthesized in the shell gland pouch. The blue color is produced by biliverdin; the brown color is produced by protoporphyrin, and they are incorporated into the shell in different ways based on their different compositions. Green eggs (with both blue and brown pigments) are exceptionally hard to candle--harder sometimes than even some very dark brown eggs like those of Marans or Welsummers.