The CIELAB color space, also referred to as L*a*b*, is a color space defined by the International Commission on Illumination (abbreviated CIE) in 1976. It expresses color as three values: L* for perceptual lightness and a* and b* for the four unique colors of human vision: red, green, blue and yellow.

The letters L*, a* and b* represent each of the three values the CIELAB color space uses to measure objective color and calculate color differences. L* represents lightness from black to white on a scale of zero to 100, while a* and b* represent chromaticity with no specific numeric limits.

To decode a sRGB encoded color, raise the rgb values to the power of 2.2 . Once you have decoded the color, you are now free to add, subtract, multiply, and divide it. By raising the color values to the power of 2.2 , you're converting them from sRGB to RGB or linear color space.

CMYK is the smallest colorspace. RGB is a larger colorspace, but is still device dependent. LAB is a colorspace that is device independent, and accounts for every human perceivable and non-perceivable color.