1) as applied to video systems, short for red, green, and blue, three color signals that can between them create a complete video image; most computer graphics systems use this tri-color approach; early models of the IBM PC uses TTL RGB, which allows the color signals to take on only a few discrete values; most computers now use analog RGB, which allows the color signals to take on a continuous range of values; 2) as a color model, a method of representing all colors as the combination of red, green, and blue light that would create color; 3) a characterization of video systems that work with picture information carried on three signal (red, green, blue) lines rather than combined in a single line (composite color).