The Lab colour space comprises all colours perceptible to the human eye. In this 3D colour model, the L-axis is a correlation of lightness, the a-axis relates to redness and greenness, while the b-axis describes the colours from blueness to yellowness. The Lab colour space serves as a device-independent model. The colours are defined regardless of their method of production and their output technique. The Lab colour space is arranged in equidistant gaps, i. e. the larger the difference between the colours within the colour space, the more clearly the difference can be perceived with the human eye.