red mold?

We recently found that water was running from the upstairs showers into the kitchen cupboards. The kitchen cupboards are not enclosed, they have no back. The back of it is just the wall of the kitchen. When we emptied all of the dishes from the cupboard, we noticed red spots on the walls. When we used bleach on the spots, we revealed more red...which runs all over the place. We aren't aware of the walls ever having been painted red and this is the only cupboard we notice the red walls in. My mother is afraid of it being mold or something, is this even possible? Or is it most likely that the walls were painted red decades and decades ago and just starting to show through in this area? Ever since we had the house over 30 years ago, the walls have been white in the cupboards. I have attached pictures of the spots and then of the red area after bleach was used. Thanks!