Color measurements are assessed against the CIE L*a*b scales which attribute numerical values to color and therefore allows easy comparison of colors and/or color change. As detailed in the diagram below, the L-scale measures light vs dark, with the a-scale measuring red vs. green and the b-scale measuring yellow vs. blue.

Common Standards

ASTM D1003-07—Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics