The short simplistic answer – True Ameraucana, Araucana, and Cream Legbar will all lay blue eggs.
The more complicated answer – Not many of those are really pure.
The Cream Legbar are fairly new to the US, not real common, and fairly expensive. Good luck on finding one of those that you can afford.
The Ameraucana and Araucana were developed from EE’s that originated in Chile. One of the requirements of the breeds is that they lay pure bleu eggs, no green at all. So if you can find someone that is breeding true Ameraucanas or Araucanas, you can get some pullets that are guaranteed to lay blue eggs. That’s not as easy as you might think.
When a chicken is judged at a chicken show, the judge does not see the color of the egg that the hen lays. Of course roosters don’t even lay eggs. There are some people showing these chickens that don’t quite lay pure blue eggs. If you can find a breeder that is actually breeding for pure blue eggs as well as the other characteristics, then you can get chickens that lay pure blue eggs. That’s your best bet. Find an ethical breeder. And try to get a look at the eggs they are laying.
The hatcheries don’t even come close. The generally advertise that the eggs can be many different colors. You’d have to be extremely lucky to get a hen from a hatchery that truly laid a pure blue egg even if the call their chickens Ameraucana or Araucana.
I know I’m not sounding very encouraging. There are people out there breeding for pure blue eggs. Good luck on that search. You might try contacting the Ameraucana or Araucana Breeder’s Club and fined someone if Florida that does produce pure blue eggs. A lot of those people are pretty passionate about what they are doing and blue eggs could be real important to them.
A story from my experience. I got some hatching eggs from a lady that is part of a group developing a new color/pattern of Ameraucana, hoping someday to get that new color/pattern officially recognized. About 15 generations back, they introduced some brown egg genes to get certain color/pattern genetics in the mix. Green is just brown on top of blue. For 15 generations they have been trying to get back to the breed requirements.
The hatching eggs I got from her were all a beautiful blue but about 1/3 of the pullets I got from those eggs laid an egg with some green in it. Either the rooster had some brown genes in him but more likely there are some recessive genes they haven’t been able to get entirely out of the mix.
I’m not disrespecting the true breeders at all. What they do is hard frustrating work.