It's an Easter Egger (not a breed) but a special kind that originates from crossing a dark egg layer with a blue or green egg layer, resulting in an olive egg, and in future generations resulting in a deep avacado/olive green, or a weird greenish choclatey color, or a golden brown color, and so on. . .
The main thing is, it's an EE but with dark laying parents. Which, is something a lot don't understand, as the trend these days is crossing any brown layer (like Orpingtons for example) with a blue or green layer and calling them Olive Eggers. Originally, it has been from crossing something like Marans or Welsummers with blue/green eggers.