how do eggs get colored different

[BigBlueHen53]

I had hoped @aart might tell us where in the body the different colors take place. I believe I have read a post of hers explaining this but I don't remember the details.

 

[aart]

I had hoped @aart might tell us where in the body the different colors take place. I believe I have read a post of hers explaining this but I don't remember the details.

Sorry, I don't know.
Might have been @Ridgerunner .

Did you see, and read, this link?

I posted about egg color genetics here. https://www.backyardchickens.com/threads/understanding-egg-color-genetics.1445199/

 

[BigBlueHen53]

Did you see, and read, this link?

I tried.

 

[Ridgerunner]

I'm not sure since that's almost the default color (the bile colors the shell as well, just all the way through) but I always just assumed white was calcium's default color

Yeah, I'm trying to figure out how to explain this. Many of the genes we talk about are not really either-or. They are more this or not-this. The blue egg shell gene for example. Since blue is dominant, if just one copy of the blue egg shell gene is present at that gene pair the hen will lay a blue or green egg. If the blue gene is not present then the hen does not lay a blue or green egg. That not-blue gene does not force the hen to lay a white egg, it allows other genetics to control that.

It gets more complicated but you can think of the barring gene the same way. Since the barring gene is dominant it will have an effect if it is present. If both genes at that gene pair are the not-barred version then it has no effect. That does not force it to be a solid feather, it just does not interfere with other patterns. That feather can still be penciled, mottled, solid or something else. If barring and some other pattern genes are present you can get some interesting results.

i was just wondering about how hens make their eggs different colors
im curious how that works i would love to become either a vet or zoologist

Then you will go into a lot deeper detail than I ever could. I'll go through what little I think I know below. It is purely genetics.

The basic egg shell color is either blue or white. To the best of my knowledge the reason the default is white is that it is the color of calcium and there are not other genetics (with one exception, there are always exceptions) that interferes with that white color. If you open the egg and remove the membrane inside you can see the base color.

I've read a couple of different things about exactly how that blue pigment is made. Some sources say it is made from bile, others say that it is made by the same chemical process that caused bile to be green. I'm not sure which is correct. The raw material for that blue is recycled red blood cells. Red blood cells are constantly wearing out and dying and are constantly being replaced. So the raw material, dead red blood cells, are always available.

If the blue shell gene is present it causes the calcium to be colored blue as it is being deposited in the shell gland. The shell is blue all the way through.

Brown is controlled by a lot of different gene pairs. Some are dominant genes, some recessive. Some are partially dominant and some only react when other specific genes are present. At least one of these is sex linked, passed on by the father but not the mother. One acts as a bleach and blocks the effects of a certain "brown" gene. These genes can go together in a tremendous number of different ways, that's why you can get so many different shades of brown or green.

The raw material that forms the brown pigment is the same as the raw material that forms the blue, recycled dead red blood cells. I do not know where that brown pigment is created from those blood cells any more than I know where in her body the blue pigment is created. Is it in the liver, the shell gland, or somewhere else? I don't know.

The base color, white or blue, is present as the shell itself is being formed. A brown egg is the brown pigment being laid on the top of a white egg shell after the shell has been formed. A green egg is from the brown pigment being laid on top of a blue egg shell. This generally occurs in the last half hour the egg is in the shell gland before it is laid. If you scrape the top brown or green color off you can see the base color underneath which show that it is laid on after the egg shell ifs formed. It should be the same color as looking inside the egg.

Now to the exception I mentioned. There is at least one gene that tints the calcium as it is being deposited. There could be more. It is highly likely all those gene pairs that affect brown shade have not yet been identified. It is not a major change in color but if you see it side by side with a pure white shell it is clearly noticeable.