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Why are Some Chicken Eggs Blue? All About Shell Color

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October 31, 2013

Chicken eggs come in many different colors
Chicken eggs come in many different colors

Growing up in New England,  I lived across the street from my grandparents’ chicken farm. I am not exactly sure which breeds they raised, but from photos I’ve seen, they looked to have a flock mostly consisting of Rhode Island Reds and Australorps. Both brown egg-layers.

Around our house we knew the saying ‘brown eggs are local eggs and local eggs are fresh.’ I knew that there were brown chicken eggs (from our grandparent’s farm) and white chicken eggs (from the supermarket). It wasn’t until I dove back into chicken keeping as an adult several years ago that I learned that some breeds of chickens lay blue eggs, green eggs, and even pink eggs.  

I now raise many breeds of chickens and love having a colorful basket made up of the different eggs collected from them. Since I was interested in finding out WHY different eggs are different colors, I have done a bit of research into what exactly causes this. It’s actually pretty fascinating stuff!

White Eggs – All chicken eggs start out with white shells made primarily of calcium carbonate. No matter what breed the chicken or what color an egg ultimately ends up being, all eggshells begin as white.  The white egg-laying breeds, including Leghorns, Andalusians, Catalanas, Lakenvelders among others, don’t possess any pigment genes, so they lay white eggs. Because Leghorns were specifically bred to eat little and lay a lot, they were the darling of the commercial egg industry and thus the reason why most store bought eggs were primarily white  … until recently. The perception that brown eggs are fresher and more nutritious (neither true, by the way!) has led to  the introduction of brown eggs to grocery store chains in recent years.

Brown Eggs – The brown egg layers such as Rhode Island and New Hampshire Reds, Australorps, Buff Orpingtons, Delawares, Brahmas and Plymouth Rocks, possess brown pigment genes and a brown ‘dye’ is applied (by the hen of course!) to the eggshell fairly late in the laying process; around the last 4-6 hours of the total 26 hours it takes to form the egg. This results in a brown-shelled egg. Interestingly, the inside of a brown egg is always white – the brown dye doesn’t penetrate the shell, leaving the inside the original color.

Note that the inside of a brown egg is white, while the inside of a blue egg is blue.
Note that the inside of a brown egg is white, while the inside of a blue egg is blue.

 

Blue Eggs – There are three breeds that lay blue eggs: Ameraucanas, Araucanas and Cream Legbars. The blue color is created by oocyanin, which is applied early in the laying process. The blue pigment goes right through the shell, unlike the brown pigment. So blue eggs are blue inside and out.

Green Eggs – Green egg-layers, such as Easter Eggers and Olive Eggers, are created by cross breeding a blue-egg-laying breed and a brown-egg-laying breed and those hens possess both blue and brown genes. Therefore the eggshells are green on the outside (created by mixing blue and brown) and blue on the inside, having been ‘painted’ with both blue and brown dye.

Varying shades of browns and greens are for the most part dictated by the breed laying the egg, although within a breed, there might be some shade variation. Some brown-egg-laying breeds apply less brown pigment to the shell than others, resulting in light tan eggs. Some breeds lay extremely light-colored eggs, such as Faverolles and Light Sussex, that can look almost pink or cream in color. Other breeds, such as Marans and Penendesencas, lay extremely dark brown eggs.

Having a colorful egg basket is just one more benefit to raising your own backyard chickens. Knowing why eggs come in different colors is fascinating. So why not add some color to YOUR egg basket when you choose your breeds this spring?

Add some color to your egg basket!
Add some color to your egg basket!

(Of course when choosing breeds,  you should make your final decisions based on temperament, hardiness, and other breed characteristics relating to your climate and location, not purely based on egg color.)

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Lisa Steele is the author of a natural chicken keeping book called Fresh Eggs Daily: Raising Happy, Healthy Chickens...Naturally released in October 2013. As a fifth-generation chicken keeper and ve...