Fargo 84061 YMCFK ribbons consist of yellow (Y), magenta (M) and cyan (C) panels for printing a full spectrum of colors by combining the colors using varying degrees of heat. The F panel is a fluorescing panel that allows you to print grayscale text or images that are only visible with ultraviolet (UV) light. The K panel is a black resin panel, typically used for printing text and barcodes.