Thank you! They are beautiful birds and very friendlyCould be one of your black chickens is an Americana or mix. I used to have a black hen that looked liked an Australorp except for the feather Tufts on the sides of her head and she layed big greenish blue eggs.
Araucaunas and Americanas and are breeds with black variety feathers that can lay blue-green eggs, among other colors including brown, yellow, white, and pink. If your hens have any Araucanan or Americanan genetics, that would be a fair explanation as to why the eggs might be that color.
Like many have said you have an Easter Egger! I can't help much further than that but CONGRATS on your EE!I have 6 black hens with a green tint to feathers and 1 Rhode island red. One of them is laying a blue egg and I can't figure it out. I thought only a few breeds laid blue eggs.