Pink Mold is actually not a type mold or mildew. It is caused by airborne bacteria called Serratia Marcescens.
Due to its ubiquitous presence in the environment, and its preference for damp conditions, S. marcescens is commonly found growing in bathrooms (especially on tile grout), where it manifests as a pink discoloration. Application of a diluted bleach-based disinfectant may be used to treat the affected area.
When pink mold occurs over water-based acrylic coatings, a partial delamination of the coating may be observed over heavily discolored areas. Since S. Marcescens requires moisture to thrive, the concentration of pink mold is greater where there is ponding water.
Pink mold can thrive over solvent based roof coatings also (left). Since these coatings have greater ponding water resistance, the coating remained intact.
Pink mold on roof coatings appear to be cosmetic only and remain on the surface of the membrane.