Thanks! This was very helpful! It’s what I figured but wanted confirmation from ones that know more than I doProbably with the blue gene. It dilutes black to a gray color, and affects all black on the chicken.
So a chicken that would be all-black can become all blue (gray). But a chicken that would have a black tail, or black lacing, or black spangling, or a black breast, can have those areas turned blue, like in the case of your hen.
At the present time, I think most EEs are not direct crosses of Ameraucana with anything else. They typically share ancestry with Ameraucanas, and have many traits in common, but are just bred to each other.
She probably did not get the coloring from any purebred parent, just from whatever genes were available in a flock of many-colored Easter Eggers.
I would expect a bunch of mostly-black chicks, and a bunch of mostly-blue chicks, about half each way. All of the chicks would have a chance of showing bits of gold, or bits of silver (white), as they grow up. All of the chicks would carry the lavender gene ("self blue"), but would not show it.
The "black" chicks are what normally occur when a black or lavender (self blue) chicken is bred to another color. Your hen will pass the blue gene to half of her chicks, and the gene for not-blue to the other half of them. This is why half will be blue and half will be black.

