I’ve checked several times because it has worried me, but it seems to just be darker colored fur and the pinkness of the skin making it look like that. Bub’s paws are like that too and you can only see it when the pads are spread apart (like in that picture where Bailey had her toes pressed into the ground). Neither of them act like their paws bother them.
Bub and Bailey’s vet had a corgi named Water (named when his son was 2 years old). Today when Bailey went for her shots the vet’s son was there and said, “She looks just like Water!” After that he got quiet and looked very sad. His mom then explained that Water had recently met an untimely death. I never met Water, but I would hear about her when we made trips to the vet. Her personality seemed to be very much like Bailey’s. I know she’s missed terribly by her family. RIP Water.