No colored sheep except tons of pink.

The normal amount of grey/light grey sheep that normally spawn were all pink. I was in a swamp biome and there were an abundance of sheep. There were more than I had ever seen, and about 1/4 of them were pink. I also could not find any cows. The cows are most likely just my fault, or due to the abundance of sheep. I killed all the pink sheep and collected 18 pink wool.