Mold grows on almost ANY SURFACE given the right temperature, humidity, and food sources.

Below is a photo of a home infestation on interior walls. Mold can grow on the insides of walls, in crawl spaces and vents, and even on carpets and upholstry and can be almost any color.

Below is a collection of photo and article links to mold-help.org demonstrating various types of mold growths.