Maybe Serratia marcescens, a bacteria found in soil, on animals, and on food, pretty much everywhere. It grows especially well in toilets, on tub wall, on food, on laundry, in ice machines, etc. It loves to eat shampoo and soap residue in bathrooms for the phosphorus they contain. It leaves a pretty pink, pinkish orange or orange red stain. You live with it every day all day. It's the pink slime in your dog's dish, your shower, and your toilet.

Fun fact: it is in the same family, Yersiniaceae, as the Black Plague, but with nowhere near the result.

Or maybe someone dropped a red Jolly Rancher, and the ice is coloured by that.

Probably one of those.