and a developmental and cultural construct.
Our eyes detect a tiny range of the electromagnetic spectrum...about the width of one blade of grass on a football field. Why that range? Well, we just happened to be associated with a star of a type that emits most of its energy in that range. We audaciously call the range of electromagnetic radiation we perceive 'light'...so, everything else is 'dark'? We live on a planet with an atmosphere consisting mostly of nitrogen and oxygen, which scatter photons of particular frequencies in 'light' that we call 'blue' or 'blau' or 'azzurro' or 'अश्लील'. As very young children we learn that the sky is 'blue'. When we are shown 'blue' things our brains are active in particular areas in particular ways.
Our brains create colored percepts of our visual field about 10 to 12 times per second, but there is really no known experiment that can prove or disprove that two individuals per experience the same or different 'colors' in the percepts their two brains create. Whatever our brains show us can only (at least in current science) be characterized by brain activity and by the culturally defined words a person uses to describe the percepts of their brain.
= new reply since forum marked as read