The darker one is almost certainly a rooster, and the lighter one is almost certainly a hen. They will molt out many times before they get their final color in, so don't worry if its not perfect at this age. Many Dorkings will have one fifth toe that is larger than the other, and some of the males have very large fifth toes. It's only a concern if it's so large that it interferes with walking, or is longer than his spur and at the same angle (he can break his fifth toe while flogging someone, although hopefully he'll be so sweet you'll never see that). Sometimes the fourth toe can be a problem, if it points down at such an angle that it puts too much pressure on the tip while standing. I had one cockerel that I was trying to decide whether or not to cull him. He was a sweet lap chicken, had some nice conformational traits, but was a little small. Then he injured the tip of his fourth toe -- not a serious injury, but despite appropriate medical treatment I couldn't get it healed. Eventually it became infected and painful. The angle was almost straight down, and it pressed into the ground with each step. Eventually that was the deciding factor, as I didn't want to propagate that trait, and I would have had to amputate the toe to make him comfortable.
If you decide to breed over multiple generations you will eventually want to select for things such as size and angles and attachment sites of the forth and fifth toes, but with only one of each gender to select from, at this point you just want to make sure that their feet are functional. If you do continue breeding you'll want to prioritize you selections in the following order. First, be sure everything works well and the bird is vigorous and healthy. Second, remove any birds from your breeding program with any genetically dominant disqualifications (such as side spurs on the comb). Then select for conformation (also called frame, which is the shape of the body), then size (because most Dorkings in the U,S. are quite undersized), then feet and face details (toes, comb, wattles, head width, etc), then color is last on the list. There are numerous breeds that are the same color as the Silver Grey Dorking (which is the basic silver duckwing pattern), but it's the other features that make the breed unique. And while it's not listed as part of the breed requirements, many breeders also select for a good temperament, since that's a part of the breed's reputation than we all want to preserve and enjoy.
Enjoy your Dorkings. They're a wonderful breed.
