Shade is measured using the L, a, b system. L measures the whiteness on a 0-100 scale. It is similar to brightness. The “a” value indicates the red-green component of shade, with positive values being more red and negative values being more green. The “b” value indicates the blue-yellow component of shade, with positive values being more yellow and negative values being more blue. Shade is generally measured according to TAPPI Test Method T524.