The fungus/mold Aspergilus niger is dark brown or black. The pigment is probably some form of melanin, the production of which uses L-DOPA made from L-Tyrosine by the enzyme tyrosinase. I don't know that I have ever seen a culture of A. oryzae, so don't know if it also makes a melanin-like pigement.

We used to live in a house that had a big pecan tree beside the driveway where I parked the car. At a certain time of summer, the tree had a heavy infestation of aphids which secreted a sugar-rich liquid "honeydew" that fell onto anything beneath the tree. My light tan car would grow nice little black colonies of A. niger in the aphid juice unless I washed it weekly. If I postponed washing it for as long as two weeks, it would become almost completely covered by the black mold, especially on summers when the aphids were especially numerous.

Robert