I didn't think it would do that either, but it was the only thing that had changed prior to seeing the pink color. It didn't happen overnight, but over a period of two or three months of regular use.I've fed a lot of breeds Calf Manna over 50 years, and I've never seen it turn feet pink. There is not enough dye in there to do that. Feed some scratch, or cracked corn, and see what happens.
Of course we could just have weird birds too and it was simply coincidence.