I’m pretty sure a lot of the discoloration comes from pigments/microplastics from the clothes rubbing against the wall. Look how dark the shoulders of these “gh

I’m pretty sure a lot of the discoloration comes from pigments/microplastics from the clothes rubbing against the wall. Look how dark the shoulders of these “ghosts” are. If it were just grease, you’d expect the head part to be darkest.