Colour science 101
All modern colour displays are built on the foundation of CIE colour matching functions, which are the practical application of much colour science. These CIE colour matching functions allow us to exploit metamerism by performing a lossy transformation from a spectral power distribution (SPD) into a triplet of values that represents how a human would perceive the original stimulus. This is done by transforming the SPD into the intermediate, unitless, linear CIE XYZ colour space.
The XYZ colour space has one very important property that is good for a game developer to understand: the Y component represents relative luminance. Luminance is a human perception SI unit that is measured in candela per metre squared and can be understood simply as the brightness of a colour stimulus. This XYZ colour space allows us to adjust this relative luminance independent of the colour by changing the Y component. The other important thing about this linear XYZ colour space is it can be easily transformed t