The silver Sussex is not a common color here in the US, I have never heard of it until now, but judging from the pictures provided the first hen is not a purebred Sussex at all as they have white shanks and she has black shanks. The solid black is not a Sumatra as she doesn't have the correct body type nor does she have dark enough skin.
Most of us have come to the conclusion that they are mixes. And most likely brown egg laying mixes at that, as there is not significant evidence that they will lay blue eggs.
