This is the great conundrum with Ameraucanas. Technically, they are purebred when it comes to genetics but not according to the SOP.
There are two ways to look at them.
If you look at them as a breed all ameraucanas lay blue/green eggs, have peacombs, and slate color legs. If they come from a mix of purebred AMS they should ALL have at least those qualities.
If you look at them according to the SOP established by breeders they would be EEs.
Breed standards say blue eggs only, for whatever that's worth.