Whether you buy your eggs fresh from a market or raise chickens yourself, you might have been surprised the first time you grabbed an egg that wasn’t white or brown–which are the options most of us see in the supermarket.

The truth is that eggs can come in a wide variety, of colors…but why?

It has a lot to do with a chicken’s genetics, says a poultry expert from Texas A&M AgriLife Extension Service. The birds themselves are provided diverse color patterns for purposes like camouflage, protection from predators, and as a way to identify each other, and their eggs usually follow suit.

For example, Leghorn chickens typically lay white eggs, Orpington’s lay brown eggs, and Ameraucana lay blue ones.

No matter their color, all chicken eggs are similar in taste and nutritional composition.

A fun fact from Dr. Gregory Archer, a member of the Department of Poultry Science at A&M: a chicken’s earlobes often predict their egg color.

“Generally, hens with white earlobes will produce white eggs. But all eggs start out white because the shells are made from calcium carbonate. They get their color from the hen’s genetics as the egg forms.”

The different colors come from pigments that are deposited onto the shell as it forms in the hen’s oviduct. Hens make and lay an egg in around 24 hours. The pigments generally are deposited too late to penetrate the shell, which is why the inside of most shells remain white.

Speckled eggs are a bit different, because those spots are just extra calcium deposits and not genetic material. The only difference between specked shells and others is that their shells tend to be the slightest bit stronger.

Other factors, like environment, the age and diet of the hen, and stress can also affect color, according to Archer.

“As they age, hens that lay brown-colored eggs may start to lay larger and lighter-colored eggs. But though this may produce an egg of a lighter or darker shade, it will not alter the egg’s basic color.”

The same factors can also occasionally affect size and shape.

“Stress factors like disease, heat or overcrowding may also affect the hen and impact the size, shape, and quality of the egg. A lot also depends on the amount of calcium the hen has in its body and can provide for the egg-making processes.”

The color of the shell does not affect the yolk color, but a hen’s diet can change a yolk’s pigment, as well. Hens raised on a plant diet tend to produce yellowish-orange yolk, while corn or grain-raised hens produce pale yellow ones.

Pasture-raised hens do tend to have yolks that contain more omega-3s and vitamins, and less cholesterol, so it appears there is something to be said for eating eggs from happy chickens.