In colour images, the number of colours used to represent the image. Typical values are 8-, 16- and 24-bit colour, allowing 256, 65,536 and 16,777,216 colours to be represented. The latter is known as true colour, because 16.8 million different colours is about as many as the human eye can distinguish. Devices that support 32-bit colour use an 8-bit alpha channel to define a possible 256 levels of opacity. Also referred to as colour depth.
