There's some information in F.B. Hutt's book, The Genetics of the Fowl.
It was published back in 1949, and someone republished it more recently, but buying a copy in print costs a lot more than I think any book should :D
Ooh, I just found it online here :wee...
Sounds a lot like what I've found.
None of these affect your egg color project, but I'll list the other effects and interactions I can remember reading about.
Genes with other effects:
--homozygous pea comb makes smaller wattles and a bare line on the breast
--beard makes smaller wattles...