(n.) A display monitor capable of displaying many colors. In contrast, a monochrome monitor can display only two colors — one for the background and one for the foreground. Color monitors implement the RGB color model by using three different phosphors that appear red, green, and blue when activated. By placing the phosphors directly next to each other, and activating them with different intensities, color monitors can create an unlimited number of colors. In practice, however, the real number of colors that any monitor can display is controlled by the video adapter.
Recommended Reading: Webopedia’s The Science of Color.