Thanks! Actually, I think Olive lays little white eggs. It's hard to tell sometimes who lays what. And Persephone is greyer, so I think she's a Cuckoo Marans.
Okay, you're last two pictures didn't show up. The top picture is a Barred Rock (sometimes called Barred Plymouth Rock), but the chicken your described sounds more like a Dominique, which has a smaller (rose) comb and less distinction between the black and white.