That would be a good place to ask.
Personally, I've heard the same thing (dilution of red, not fully understood), and I don't know beyond that. Well, I know that buff is pretty to look at, but that doesn't help with the genetics of it!
Every one of those involves a dominant gene. Once those traits are bred out, they will not come back unless someone re-introduces them to the line.
But since the Silkie hookless trait is recessive, it could hide in a line of chickens for a long time, and pop up in 1/4 of chicks every time two...
I read somewhere else that one gene is dominant (makes the feathers keep growing, rather than stopping at a certain length) and another gene is recessive (prevents the tail feathers from molting each year, which means they get longer overall).
Oh, maybe this is where I found it. This page has a...