CIE L*A*B*Colorspace

International Commission on Illumination

LAB Colorspace

A Lab color space is a color-opponent space with dimension L for lightness and b for the color-opponent dimensions, based on nonlinearly CIE XYZ color space coordinates.

CIE Lab Colorspace:

L is always pasitive and represents brightness
a>0 represents red conponent, a< 0 green conponent
b>0 represents yellow conponent,and b <0 blue conponent