The grey one is absolutely stunning, might have some breed in them because grey isn't such a common colour for barn and stray cats.
I also have two stray kittens and one of them is semi-grey, no she doesn't have grey hairs between her black hairs but (hopefully) once a year she turns almost completely grey she became grey when she was about 6 months and then turned back to black so i'm hoping she will turn grey again soon.