Update: now that the girls are grown, I can tell that the black one turned out to be a Black Australorp, and the white one is definitely an Easter Egger of some sort. She lays me a green egg almost every day. Thanks everyone for your help!
Part of our recently inherited flock included these two. They look to be the same breed, just different colors. I can't figure out how to even do a search to start looking. I have narrowed their age down to 15-19 weeks.