They're one litter, since they were all adopted from the same source/newborn on the adoption page, and clearly share a design c:
The blankets just happened to indicate early what kind of outcome(s) you'd get, similar to newborn 2nd Gen pups. (The October litter only had different blankets, though; the pups themselves all looked the same, unlike 2nd Gens.)
There's been quite a few litters on CS that developed similarly.
The first to do this were the
August 08 Balloon dogs, with pink, blue and purple blanket designs for the three outcomes.
Equimagine horse litters were depicted by horseshoes on the adoption page, and after adopting you ended up with
several different newborns which often grew into only one or two outcomes, so you knew fairly early if you missed anything. (There's exceptions, though, like the
RBM litter, which was a nightmare to keep track of xD)
And quite recently there was a
butterfly wolf litter that gave you yellow, red and blue caterpillars.