Pink stains on my kitchen counter

[Alabamian]

There is an unusual, very bright pink stain that shows up on my Corian type kitchen counters. It is usually in an area where water has been on the counter, but I have used nothing this color in my kitchen - in fact, I usually see it first thing in the morning, after nobody has even been in the kitchen. I've also found it in the sink and on my dishrag and sponge, which leads me to believe that it has something to do with the water. The stain is very difficult to get off the counter, but the main thing that's bothering me is wondering where in the world it comes from and if it could signal some kind of impurity in the water - please if anyone knows, share!!