Edit 2017: This was the first thing I ever wrote about color. I’m older and wiser and I wanted to issue a few disclaimers. Understanding the foundation of CIE colorimetry is very practical but here are some things to remember.
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This blog post is an introduction to the CIE 1931 color system, an international standard model of human color vision that is used all around you. Do you see any color prints around you? Are you reading this on a color display? All of that is made possible by CIE 1931.
Commission internationale de l’éclairage (CIE) is a 100 year old organization that creates international standards related to light and color.
CIE 1931 is a Color Matching System. Color matching does not attempt to describe how colors appear to humans, color matching tells us how to numerically specify a measured color, and then later accurately reproduce that measured color (e.g. in print or digital displays).
To reiterate that point, Color Matching Systems are not focused on describing color with qualities like hue or saturation, they just tell us what combinations of light appear to be the same color to most people (they “match”). Color matching allows gives us a basic framework for color reproduction.
You can think of CIE 1931 like you would Newtonian physics. It’s a mathematical generalization of human color vision, that allows us to define, and accurately reproduce colors in most situations. It does not fully describe the subjective and complicated process of human color vision, it’s not without edge cases, but it is relatively easy to work with.