EE chickens come in all colors.
From my understanding is that hatcheries subcontract out the egg laying. So it all depends on what that farmer has as stock. They may be purebred but more than likely cross bred. We learned a lot taking EE to a breed show in our state last year. So this year we bought ours from a breeder in our state. There is a huge difference between hatchery vs breeder birds.
Our EE chickens are all different in their color patterns. We have had all white w/ green legs, sliver colored, black and white, black, white, brown, green legs, blue legs. Blue eggs, green eggs, olive eggs, pink eggs, and brown eggs. Single comb, pea combs, and walnut comb. With muffs and without.
If you check out the APA website there are breed standard of perfection for every breed.
True Ameraucanas have 8(?) different color patterns, and guidelines for every aspect of them. The eggs are blue. Legs are also blue.
IF your EE chick was hatched without a muff it will never grow a muff later on.