Refers to use of paper other than white and ink other than black. Computer monitors use the RGB color space and most printers use CYMK. Most color problems stem from either poor translation between these color models, limitations in one of the color models (out of gamut colors), or poor color separation. Also common is spot color, in which black ink is supplemented with an additional color. One way of ensuring that color fidelity is maintained across the design and printing process is to use a standardizes set of colors, usually from the Pantone Matching System.