I’m not sure how only white shelled eggs being sold in supermarkets came about. Probably something to do with white equaling purity in the psychological minds of America. But until maybe 15 years ago, the supermarket shelves were only lined with white shelled eggs.
However, since the “organic” and “free-range” labels have come along, brown eggs are now synonymous with healthy and organic. (The organic label itself is problematic; but that’s another complete blog post.)
But science be told, brown and white eggs and green eggs — yes, green eggs — are all equal in nutritional value. Well, that is if the hens eat the same food. Hens eat everything from grass to insects to commercial chicken feed. Healthy chickens require a far more diverse diet than massive factory farming provides and that’s one of the reasons why those brown shelled eggs often have thicker shells. Those small farm hens get better nutrition.
So what determines the color of the egg? The breed of the chicken. White and light-feathered chickens like the Leghorn tend to lay white eggs, and brown and dark-feathered chickens such as the Rhode Island Red mostly produce brown eggs. Green eggs are from a specific kind of chicken called an Araucana, which are uniquely popular among hobby ranchers. Genetics. Simple as that.
Next time you’re in the supermarket, don’t pick the eggs based on their color. It doesn’t matter. Instead, I’d suggest heading to the farmer’s market and asking your local farmer what the names of his/her chickens are.