I personally love chicken color genetics. I suppose the first thing you should learn about is the foundation colors.
The foundation color of any chicken is determined by the 10 E locus series base colors. Poultry Genetics.
The E locus genes, in order of most dominant to most recessive. Genes:
1. E(dominant black/extended black)- examples of this base color can be found in many breeds, from the black Australorp to the white crested black polish. Dominant black is very common. But every black chicken is NOT dominant black, and dominant black chickens aren't always black either, for example my paint silkies are E-dominant black, but they appear mostly white thanks to I-dominant white. There are also black dilutions; Bl-blue, lav-lavender, choc-chocolate. Furthermore two copies of c-recessive white covers black and red pigment. Also, while E-dominant black hens are usually free of color leakage, males are the other hand will commonly have red, gold, or silver leakage on their necks, shoulders, and/or body feathers. Chickens that are solid black without any leakage were selectively bred to avoid color leakage, and black based chickens commonly have black enhancers.
As for black chickens that aren't dominant black, a birchen with a Ml-Melanotic gene appears solid black, as is seen in the FBC Marans, which is why Some FBC Marans are completely black. Note that many FBC Marans blood lines were also mixed with black Marans, so some FBC Marans flocks are actually a mix of ER-birchen and E-dominant black and Ml-melanotic. However, the FBC Marans aren't supposed to be dominant black, but you can't tell the difference between a E-dominant black bird and a ER-birchen + Ml-melanotic bird that appears all black, so it would be hard to enforce the idea that E-dominant black shouldn't be allowed in FBC Marans lines, when, Ml-melanotic is considered to be a trait of the breed variety, and it would be hard to breed out the E-dominant black and leave the Ml- melanotic gene. As they are both dominant and it could be hard to distinguish between the two. Another black enhancer that can make a birchen base bird appear solid black is cha(charcoal).
2. ER(birchen), FBC Marans are considered to be red birchen, but there are many breeds that are birchen that better represent this base color, birchen Cochins are a good example. Birchen chick down is similar to a E-dominant black chicks down, birchen chicks are usually mostly black with a few white or off-white spots on their wings and under belly. Birchen is a common color.
3. ER- Fay(fayoumi birchen), as possibly seen in the silver and gold Egyptian Fayoumi chicken, the Egyptian Fayoumi has many alleles contributing to their appearance besides their base color, they possess pattern genes that give them autosomal barring, those genes being Db Darkbrown and Pg pattern gene. The chick down of the ER-Fay is supposed to be red-brown. This is a rare base color.
4. eWh(dominant Wheaten), think salmon faverolles, they are eWh-dominant wheaten, and they are a excellent example for this base color as the salmon faverolle doesn't have many other feather genes at play, therefore you can really observe the difference in chick down, dominant wheaten chick down is a light cream color, and while adult plumage on hens is usually are a buff or beige color, an adult dominant wheaten rooster has a similar appearance compared to other base colors, such as e+, eb, and ER.
5. e+(duckwing/wild type), the welsummer is the poster child for duckwing, Welsummers are a red duckwing. Side note; in American we commonly call duckwing partridge. So commonly it's called partridge instead of duckwing that you may think of "partridge" as meaning American Partridge, also in America we call eb-"European"-partridge, brown, and for some reason we also refer to duckwing as brown and light brown. e+ duckwing is the original base color, the red jungle fowl is gold duckwing. Duckwing is a common color, to tell the difference between e+ and eb you can look at chick down on birds that Aren't carrying other genes that cause changes in chick down, or you can tell by looking at adult females, e+ hens will have what is called a salmon breast, and eb hens chest will be a similar color brown as the rest of their body. The chick down of e+duckwing chicks, they have very uniform stripes, males will have lighter stripes and females will appear to be wearing winged eyeliner. Homozygous e+duckwing chicks can be sexed by looking at their chick down, the accuracy can be as good as 95%, but unlike the welsummer, not all duckwing based breed verities have been bred for their auto sexing potential, therefore the accuracy of sexing chicks is not going to be as good.
6. eb(partridge/brown), fun fact; brown leghorns most commonly come in e+-duckwing, they can also be actual brown, eb-brown birds will Not have a salmon colored breast feathers on the hens. The eb roosters will look exactly the same the e+ roosters, almost identical. eb-partridge brown leghorns are usually marketed as dark brown leghorns. Partridge/brown is a common color. I have many eb-partridge silkies. A lot of Easter eggers are eb-partridge as well. A eb-partridge chick without any other genes that affect chick down will look chocolate in color, with no stripes or very faint stripes. However many breeds that are eb-partridge carry pattern genes that can cause multiple variations of stripes on the chick down. It should also be noted that, the pattern gene Pg(pattern gene), will Not change eb(partridge) based roosters' juvenile and adult plumage. Currently most eb-partridge based breed varieties have pattern genes, for example the partridge rock is double laced. Ml-melanotic + Pg-Pattern gene = double laced, but this lacing will only show on the females, not the males. Furthermore eb-partridge does Not have auto sexing potential.
7. es(speckled), so I have never seen a es(speckled) base color chicken, to my knowledge any way. If anyone can prove this base color is in fact real, that would be pretty cool. All I know is that es(speckled) was used as a description for the base color for chickens in a study on chicken color genetics, so it's generally assumed that they were seeing some new traits, that they are certain are linked to their base color genes. But I can't find any descriptions of the color, so either it's rare or maybe it's very similar to another base color. One might assume that the color being called speckled would indicate that this particular E locus mutation either causes some form of speckling on the bird, or that this base color has some sort of effect on mo(mottled), or Db(Darkbrown) + Ml(Melanotic) + Pg(Pattern gene) = spangled. But this is just speculation as I can't find any real evidence that this base color exists.
8. ebc(buttercup), I can't tell the midfielder genes from the differences in the E locus mutation, but the Sicillian Buttercup is ebc-buttercup. The adult plumage does look pretty similar to most other base colors that have autosomal barring. ebc-buttercup's distinctive difference from other E locus base colors is, the differences seen in the chick down. Buttercup is a rare color.
9. ey(recessive wheaton), recessive wheaton is generally accepted to exist. But no modern breed claims to be exclusively recessive wheaton. As far as I know, the only way to tell the difference between eWh(dominant Wheaten), and ey(recessive wheaten) is though breeding. Dominant Wheaton is only recessive to dominant black and birchen, whereas recessive wheaten is recessive to either all other base colors, except, perhaps recessive, Wheaton might not be recessive to eq(queen Silvia). It is to my understanding that a recessive wheaton has not been crossed to a queen Silvia, and therefore it is not known which of the two would be expressed phenotypically. Supposedly the chick down of recessive wheaten is different from dominant wheaten as well. Recessive wheaten is considered rare.
10. eq(queen Silvia), The Queen Silvia chicken was developed by Swedish geneticist Martin Silverudd the name choice was to honor Sweden's longest reigning queen, Silvia. This is another breed that has pattern genes, among other feather color modifiers, this breed also has autosomal barring. I don't know how eq-queen Silvia differs from other E series base colors. Queen Silvia as a breed is rare and so there aren't many opportunities for getting a queen Silvia chicken, so I don't have any firsthand experience with this base color. This is a very rare base color.
