Do you mean like these I just collected.the blue is in the shell, so a true Ameraucana will have no brown genes, only the blue gene, and that blue is IN the shell, not a coating ON the shell.
Brown is a coating ON the shell.
So, for a good olive Egger, you breed an Ameraucana to a good dark eggs layer, and that chick that hatches, breed back to the same dark egg line, and you should get a very nice dark olive egg.
So.... you are line breeding the good dark egg line, and introducing a blue shell.
The Olive egg is Splash Copper Marans x Cream Legbar