Quest for Egg Color Genetics

[LTygress]

I finally found a really good link for chicken FEATHER-color genetics. And I can't recall who sent me to that link, but thank you none the less.

However, now I want to learn about egg color genetics. I hear "mint-green eggs" and "pink eggs" and then there's the blue, brown, green, and white. I can already guess that "mint green" and "pink" eggs are just pale versions of green and brown. And I believe I saw someone mention on these forums that green is actually blue with a brown overlay. Or maybe vice versa.

Anyway, I'm wondering if anyone can actually explain the genetics of egg colors, and how each color may "taint" another, or only show through in part like the pink and mint-green eggs. This may become a long thread with me asking many questions spawned off of answers to others. But please bear with me, I'm trying to fill in the blanks in my head.

If you have any corrections to the information above, feel free to share it to help me clear things up, too.

First, I'll start off with pink and mint green. Are these possibly eggs created from the brown and green layers, where the chicken was bred back to a WHITE egg-layer such as a leghorn?

 

[ChickenCanoe]

...

However, now I want to learn about egg color genetics. I hear "mint-green eggs" and "pink eggs" and then there's the blue, brown, green, and white. I can already guess that "mint green" and "pink" eggs are just pale versions of green and brown. And I believe I saw someone mention on these forums that green is actually blue with a brown overlay.
...

That's basically it.
I've done a lot of research on the subject. There is a fair amount of research on white and basic brown but not much else.

A bird with blue egg genes will create a shell that has the blue pigment in the shell, so it's blue inside too.
A green, olive and khaki egg is from a bird with the blue gene and parentage of a brown layer.

The pink/plum is a brown egg with a layer of calcium applied after the color.
There is supposed to be a breed in South America that lays pink and yellow eggs but I haven't seen them. I think it is in Peru. A lady in Canada has some but won't ship to the US. Bummer!!

I have been unable to find any research on dark brown genetics (Marans, Penedesenca, Welsummer, Barnevelder)
Of those, I've only raised Penes and Wellys. With the Penedesenca, it is my belief that the color is in the shell rather than on it - similar to the Araucana blue.
In some brown eggs the color is probably one or two chemicals. In the dark eggs, I'm convinced that there are a number of chemicals that make up the color.

 

[LTygress]

I'm getting some copper marans this coming Spring from McMurray, so around summer time, I'll be able to see if their color goes all the way through as well.

I know many people say that buff orpingtons tend to lay pink eggs. And I'd almost think that one of my bantam hens (a mix of mille fleur and ameraucana) lays yellow. Hers are a very dark off-white color with a yellow tone to it. But it's not a blatant yellow - it just looks like a really dirt-stained white.

One of the things I've always wondered, is if the egg pigment is a fading type of thing (i.e. each generation of brown bred to white gets lighter and lighter brown) or a dominant/recessive thing (a green egg bred to white gives some blue, some brown, some mint green).

 

[ChickenCanoe]

It is a fading thing in three ways.
The later in the laying season, the lighter the eggs normally get.
If cross bred, egg color will definitely go away. The blue gene is dominant though.
Even if staying within the breed, egg color will fade if one doesn't cull hard, select for color and keep good breeding records.
Most Barnevelder strains lost the dark color because it wasn't selected for.
I bought hatching eggs of 3 varieties of Marans from a farm that started with very good lines of the varieties. The eggs weren't dark at all. She had lost the color because she hadn't selected well.

 

[LTygress]

So all colors fade except blue?

 

[ChickenCanoe]

No, I think the blue will fade as well as the laying season progresses.
But since it is a dominant gene the offspring will most likely carry it. This is an oversimplification, of course.

I'm sure that nutrition plays a part in the color intensity.
Certain chemicals can't be produced if the chemicals aren't available in the diet.
It's like the old computer programming lingo, GIGO
Garbage in, garbage out.

ETA
All the colors applied to the outside of a shell or in the shell are made up of some chemicals the hens shell gland has to produce. If she has the ingredients to produce those chemicals she will, if she doesn't, she won't. As the season progresses, she seems to be less able to apply those chemicals.
She also has to have the genetic makeup for the shell gland to want/need to produce those chemicals.
Again, oversimplification.