Music is a neural interpretation of sound. Color is a neural interpretation of light—and to the brain color is primarily a subjective experience. There is no neural receptor that distinguishes any gradation of gray. It, like many other colors the human brain imagines, is a belief construction within the brain—a form of understanding. A thought. (Davidoff, J., et al. "Language and perceptual categorization." Trends in Cognitive Sciences. 5:383-387. 2001).