Kodachrome film is a B&W film with at least 9 different emulsions sensitive to Red, Green and Blue light and these emulsions are able to tell them apart and reproduce the original colors. The coatings are very thin to give good sharpness and the emulsions are very fine grained but still give good speed and grain. The coating is so complex than only Kodak remained active in this field even though Fuji once made a compatible film, as did Konica in Japan.