We do not always agree about colour. Your red might be my pink or orange. Vietnamese and Korean people do not differentiate blue from green – leaves and sky are both coloured xanh in Vietnam. The late English artist and filmmaker Derek Jarman once met a friend on London’s Oxford Street and complimented him on his beautiful yellow coat. His friend replied that he had bought it in Tokyo, where it was not considered yellow at all, but green (1).
The Dugum Dani people of New Guinea, for example, have only two colour words, which can best be translated as “black” and “white”, or dark and light. A few other pre-literate cultures recognize only three colours: black, white and red. Others have only a handful more.
There is no known culture that recognizes, say, just red and blue: you do not tend to arrive at an expression for blue unless you already have black, white, red, yellow and (perhaps) green.
We all grow up knowing that a certain frequency of light wave is red. We have no way of seeing through another person’s eyes; and therefore, no way to tell that they are seeing that colour differently. And even if they were, they were not going to identify it as e.g. “blue”. They would “see” red too… (2, 3)
The sky in ancient Greece was not blue (!!!), no matter how strange that sounds. The people in that era thought the sky was “bronze” coloured. And great differences in what people back then actually “saw”, applies for other things as well. (4, 5, 6, 7, 8, 9)
In any case and besides all the above, most of the living animals (e.g. many insects) do not “see” the colours we “see”. So if what is “real” is determined by what the majority thinks is real, all of the above refer to something which simply… is not!