Blue mold

From Freepedia

Blue mold is a downy mildew of tobacco caused by Peronospora tabacina. Blue mold can cause severe damage to susceptible tobacco in many parts of the world. Since it is an obligate parasite, it must have living tobacco tissue in order to survive.

Also, the mold Penicillium roqueforti used in producing the taste, and characteristic blue-green inclusions in Roquefort cheese.