EE's can lay any color egg especially if they are bred to other EE's of different mixes like i have a 50/50 ameraucana/sexlink and a 50/50 ameraucana/std cochin they're babies egg color can be anywhere in any specturm because of the babies colorful backround!! and on a very extreme note i have a 50/50 EE/faverolle mix she lays brown eggs but mixed with my ameraucana/sexlink roo their babies could lay pink eggs it just depends on the backround of the chicken like speckledhen said hers were of the same backround and laid two different colored eggs. and to answer your question about breeding for egg color you certainly can welsummer breeders do it, ameraucana breeders do it, marans breeders do it, arauacana breeders do it, i do it w/ my EE's its just another trait like feather color or foot feathering you can breed for just about anything if you try hard enough
