I thought all the yellow ones where Pekins but a few have started to look different than the others.
The ones that are standing more upright like the closest (and maybe the black one) are Indian Runner ducks. They can be any color. Where did you get them from? I got ducks from the farm store and ended up with 2 pekins and 3 runners. I got black ones thinking they would be cayuga or something different, but they were runners too. The runners were the most friendly though and they were very entertaining.