If they are true cories, then they are likely Bronze Cories, but they could also be Brochis splendens which is known as Emerald Catfish. My Petco sells both types and labels them "emerald green cories". They look very similar when they are at the typical pet store size.
Both of the species get large, with the Emerald Catfish getting much larger, and they should to be kept in schools of at least 6.