“If one says “Red” (the name of a color) and there are 50 people listening, it can be expected that there will be 50 reds in their minds. And one can be sure that all these reds will be very different.

Even when a certain color is specified which all listeners have seen innumerable times—such as the red of the Coca-Cola signs which is the same red all over country—they will still think of many different reds.

Even if all the listeners have hundreds of reds in front of them from which to choose the Coca-Cola red, they will again select quite different colors. And no one can be sure that he has found the precise red shade.

And even if that round red Coca-Cola sign with the white name in the middle is actually shown so that everyone focuses on the same red, each will receive the same projection on his retina, but no one can be sure whether each has the same perception.”

—Josef Albers, his great Interaction of Color, 1963. From the shiny new revised and expanded paperback edition, 2006.