Jean,
I would use the pictures of the wheaton males as a guide. They have excellent type and color. You have to imagine all of the red parts as white. As John said, you want the silver males to be only black and white. Also, look for a solid black chest. If you have several males that are only black and white, then you can pay more attention to other details. A lot of silver males seem to be high in the chest. (compare the pictures of the silvers to the wheatons) We want to have our silvers look more like the wheatons, with the deeper chest. Also, look for wide backs and rather broad head with well curved beak. Big red eyes and full beard. If I were you, I would keep 5 or 6 of the black and white ones until they get a bit older. They may still have a couple of feather changes to go through and it is often hard to tell how they are going to look as adults untill they are 6 months old or older.
Curtis