Over 20 yrs. I do work on specific colors. And when I breed for my flock, I will pair the birds or put small groups in breeding pens and mark the chicks so they are easily identifiable as offspring from the parent stock chosen.
This helps me to keep up with the lines and know what produced what. I also can tell about the parental stocks genotype by the phenotype of the offspring which is helpful if you are setting out to "work on a specific color" especially if it is a color that can be achieved my mixing genes (like artists' paints) to achieve the desired result.
