Only if we take in considerations these 4 genes at the same time we can start to look the other genes !
E-locus S-locus Ml-locus Mh-locus
Why is this so? Since there are only 2 color-pigments, Black (eumelanin) and Red (pheomelanin) as we can see in the original Bankiva fowl.
Black is determinate from the E-locus and on is best as E/E reinforced with Ml/Ml resulting in deep extended black with a green shine.
Red is determinate from the S-locus and on is best as s+/s+ reinforced with Mh/Mh resulting in a deep extended red with a violet shine.
When the Ml (Melanotic) Black enhancer and/or the Mh (Mahogany) Red reinforcer are in there original form (with a "+")
we never result in totaly Black and/or totaly Red phenotype colors. So that is the why when we ask ourselves :
"why I see restants of red on my Black birds" and/or "why there stay black in my Red birds".
If you are interested in my point of view on theoretical knowledge brought in to the practice breeding, go than to this link :
sites.google.com/site/zijdehoenders/t%26dcreating/basics-about-chicken-color-genetics-...
It is illustrated with photo's of Silkie of breeders you all know but is perfect transferable to every race of chickens.