Colorimetry, the science of how the brain perceives colour, is already being used to help people with epilepsy and dyslexia (disorders also related to brain excitablity).
This becomes useful in photometry and colorimetry as the perceived color changes with source illumination and spectral distribution and coincides with metamerisms where an object's color appearance changes.
Colorimetry techniques can be biased by color changes in test strips (from airborne or finger borne contamination, perhaps) or interference (e.g., tinting contaminants) with light source or the light sensor.
Relative colorimetry is useful in proofing applications, since you are using it to get an idea of how a print on one device will appear on a different device.