NIPPLE discoloration? No TMI

I know the breasts go through some mega changes during pregnancy. I’ve already had a kid, so I know generally what to expect.

HOWEVER, I’m experiencing something unique to this pregnancy. I’m 15w3d and I glanced down in the shower this morning to see that the tips of my nipples were like a dark brown/black/kind of green color. I’d think it was just dry skin if it wasn’t a DIFFERENT COLOR. I’m the palest person in the world, so my nipples are usually pretty pink.

Does anyone know what this is?? Or have some insight? Thanks!