The problem with many standards is that when a standard is developed it is based upon hypothetical physical attributes and not the genetics behind an attribute. The standard usually does not take into account the effects of male or female hormones upon color in a bird. One major exception being the dimorphic colors associated with male and female primary color patterns. That is one reason why individuals have a breeding pen for males and another breeding pen for females.
In order to get specific traits in a bird, the birds need to be heterozygous (split) for certain genes. Another aspect that a person must take into account is that one gene can effect the expression of another gene, this is called epistasis. There is a relationship between eye color and shank color. There is also a relationship between under color and shank color depending on the the E locus alleles (extended black (E), birchen (ER), brown (eb ) one uses to make a black bird. Here is how it works.
A person has a black bird that is homozygous or pure for brown (eb/eb) this would allow for yellow shanks and feet, a lighter colored eye and the feather under color will be white. The breeder decides that the under color needs to be gray and not white. The breeder breeds into his flock the birchen gene (ER) so that his birds are now ER/eb the under color is much darker but now some black pigment is showing in the legs and the eye is darker. These things happen because of genetics and how the genes are going to interact. The standard of perfection may not be obtainable because the genetics will not allow for the perfect standard. I think a breeder has to pick which perfect characteristics they want in their birds and will except a lesser standard in other characteristics.
There may be genes out there in the great gene pool of chickens that will make a standard perfect but the problem is that it is in another breed or variety that the breeder will never use to improve their stock- so it may not as well exist.
That is my opinion.
Tim
