Blue cheese

Blue cheese[a] is any of a wide range of cheeses made with the addition of cultures of edible molds, which create blue-green spots or veins through the cheese. Blue cheeses vary in taste from very mild to strong, and from slightly sweet to salty or sharp; in colour from pale to dark; and in consistency from liquid to hard. They may have a distinctive smell, either from the mold or from various specially cultivated bacteria such as Brevibacterium linens.

Source: Wikipedia