Whether you didn't know, cheese can be blue and not only in our Blue Cheese Sad Sticker. Several varieties of blue cheese have been inoculated with mold cultures, such as Penicillium roqueforti or Penicillium glaucum. These molds give the cheese a distinctly blue or blue-green marbled appearance and a strong, pungent flavor. Some examples of blue cheese include Roquefort, Gorgonzola, and Stilton.