Basic Chicken Egg Shell Color Genetics

Chicken egg shell color inheritance can seem complex and headache-inducing to try to figure it out. In this quick article I’ll share some visuals that I think will make it much easier to understand without having to re-visit 9^th grade biology! And once you have a grasp of egg shell genetics, you can better select what colored layers you would like to breed for. Save or pin these images to help you remember it forever!

Let’s Start With Basic Chicken Egg Shell Color Genetics

The 2 Basic Egg Shell Colors: White and Blue

Basic Chicken Egg Shell Color Genetics blue and white calcium shell inheritance — If a hen has absolutely no tint genes active, she will lay blue eggs if she carries 1 or 2 blue egg genes and white egg genes if she has 2 recessive white egg genes. The hen’s body color represents what she lays and the egg shapes to her left reveal her genetics.

Believe it or not, chickens can only have white or blue egg shells. Every single other egg color is a combination of tints laid over a white or blue egg shell.

Blue egg genes are dominant. White egg genes are recessive. If a hen inherits just one single blue egg gene, she will lay blue shelled eggs. If a hen inherits only white egg shell genes, she will lay white.

Homozygous Blue vs Heterozygous Blue

Birds who are homozygous blue (carrying two blue egg genes) typically lay eggs that are a little darker blue than hens who carry one blue and one white egg gene (heterozygous). Heterozygous hens tend to lay powder blue to very light blue eggs while homozygous hens lay bright blue to powder blue tones.

homozygous and vs heterozygous blue eggs Whiting True Blue vs Prairie Bluebell vs Easter Egger powder blue — The purebred Whiting True Blue eggs, which are homozygous blue, are shown next to Prairie Bluebell and Easter Egger eggs, which are heterozygous blue. The difference in this basket of eggs laid at the end of the season is hard to tell but the WTB eggs are a stronger blue shade.

The Dominant Tint Genes in Chicken Egg Shell Color

“Tint” or “tint overlay” is controlled by any one or more of the 13+ known genes that code for brown eggs. Tint is a type of natural colorant the hen’s body applies over the shell. In my graphics I represent tint as an egg shape with a dashed line and a brownish fill color. Tint is always dominant and always passed on, even if only very lightly.

Tint over a white egg shell will produce a shade of brown:

Basic Chicken Egg Shell Color Genetics white and brown tinted shell overlay color inheritance — The unique mixing of all 13+ brown egg genes is what codes for extremely light tints responsible for cream eggs and the extremely dark tints you see in Black Copper Marans.

Tint over a blue egg shell will produce a shade of green:

Basic Chicken Egg Shell Color Genetics white and blue shell with brown tinted shell overlay color inheritance green layer olive egger

Blue egg shell + Brown Tint = Green

We all know from painting that blue + yellow makes green but in chicken genetics, a blue shell + brown tint makes green:

blue chicken egg shell plus brown tint makes green eggs

What Happens When You Mix Colors?

If you breed blue egg layers to brown egg layers you will get all green layers. It is extremely difficult, if not impossible, to breed the brown tint out of green laying hybrids. Likewise, once brown tint genes have been introduced, it is nearly impossible to “erase” them and breed back to a solid white layer.

Green easter egger breeding egg colors — This graphic illustrates that breeding a brown egg layer to a blue egg layer just once will produce green. No matter how many times you then breed a green layer to a blue layer, the offspring will continue to lay a shade of green for many, many generations to come. Tint genes are that dominant and they do NOT easily breed out.

How to Use this Knowledge in Breeding

Once you understand basic egg shell color inheritance, you can begin breeding for all the fun colors! I’ve got articles on how to breed for various egg colors, how to breed for olive eggs, and how to breed for speckled olive eggs. There’s even a colored egg category where you can research all the different breeds, crosses and color breeding “recipes”. If you’re serious about starting a colored egg breeding program, I have PDFs for sale in my shop that can walk beginner breeders through the advanced steps required to understand and produce jaw-dropping egg colors!

a row of olive egger eggs in dark brown, khaki, olive, speckled green, jade green and blue-green shades with each generation labeled — Olive Egger breeding is fun and can produce a colorful egg basket beyond just olive tones. The letter F stands for “Filial” which means ‘generation’ and the number after it is the generation number. BC stands for “Back Cross” and the number 1 indicates it is a first generation Back Cross.

Experience is the Best Teacher

Basic chicken egg shell color genetics can seem complex but once you start breeding and seeing what the offspring lay, it can really help things to mentally click. I hope the graphics I’ve created for this post have made the genes much easier to understand and that you’re excited to begin breeding!

Basic Chicken Egg Shell Color Genetics

Let’s Start With Basic Chicken Egg Shell Color Genetics