graphics (US "color") Colours are usually represented as

RGB triples in a digital image because this corresponds

most closely to the electronic signals needed to drive a

CRT. Several equivalent systems ("colour models") exist,

e.g. HSB. A colour image may be stored as three separate

images, one for each of red, green, and blue, or each pixel

may encode the colour using separate bit-fields for each

colour component, or each pixel may store a logical colour

number which is looked up in a hardware colour palette to

find the colour to display.