“…the nature of the perpetual things consist of small particles infinite in number… the particles are so small as to be imperceptible to us, and take all kinds of shapes and all kinds of forms and differences of size. Out of them, like out of elements (earth, air, fire, water) he now lets combine and originate the visible and perceptible bodies…” (Democritus)

“Hence I think that these tastes, odours, colours, etc., on the side of the object in which they seem to exist, are nothing else than mere names, but hold their residence solely in the sensitive body…” (Galileo)

This odd notion has been passed down to us today:

“If you ask a physicist what is his idea of yellow light, he will tell you that it is transversal electromagnetic waves of wavelength in the neighborhood of 590 millimicrons. If you ask him: But where does yellow come in? he will say: In my picture not at all, but these kinds of vibrations, when they hit the retina of a healthy eye, give the person whose eye it is the sensation of yellow. (Schrödinger)

Schrödinger’s remark applies to all the “secondary qualities”:

“The world as described by natural science has no obvious place for colours, tastes, or smells. Problems with sensory qualities have been philosophically and scientifically troublesome since ancient times, and in modern form at least since Galileo in 1623 identified some sensory qualities as characterizing nothing real in the objects themselves . . .

The qualities of size, figure (or shape), number, and motion are for Galileo the only real properties of objects. All other qualities revealed in sense perception—colours, tastes, odours, sounds, and so on—exist only in the sensitive body, and do not qualify anything in the objects themselves. They are the effects of the primary qualities of things on the senses. Without the living animal sensing such things, these ‘secondary’ qualities (to use the term introduced by Locke) would not exist.The world as described by natural science has no obvious place for colours, tastes, or smells. Problems with sensory qualities have been philosophically and scientifically troublesome since ancient times, and in modern form at least since Galileo in 1623 identified some sensory qualities as characterizing nothing real in the objects themselves…

The qualities of size, figure (or shape), number, and motion are for Galileo the only real properties of objects. All other qualities revealed in sense perception—colours, tastes, odours, sounds, and so on—exist only in the sensitive body, and do not qualify anything in the objects themselves. They are the effects of the primary qualities of things on the senses. Without the living animal sensing such things, these ‘secondary’ qualities (to use the term introduced by Locke) would not exist.” (Clark)

It required a genius of my own transcendent splendor to see the obvious:

“Whatever the meaning assigned to the term complete, the following requirement for a complete theory seems to be a necessary one: every element of the physical reality must have a counterpart in the physical theory.” (EPR)

“Well, obviously the extra dimensions have to be different somehow because otherwise we would notice them.” (Green)

“Now it may be asked why these hidden variables should have so long remained undetected.” (Bohm)

“The aspects of things that are most important for us are hidden because of their simplicity and familiarity.” (Wittgenstein)

I recommend MacAdam’s ‘Selected Papers on Colorimetry - Fundamentals’; it’s a superb collection of the seminal works by Newton, Helmholtz, Maxwell, Schrodinger et al.

Also well worth it is Austen Clark’s admirable text on ‘Sensory Qualities.’

‘Color for Philosophers: Unweaving the Rainbow,’ by C. L. Hardin is a popular work and does a fine job of introducing basic psychophysics of color perception, but… someone really ought to write a rejoinder, along the lines of ‘Color for Scientists,’ as the philosophical conclusions need to be taken with a large grain of salt (think “Utah”). Hardin concludes that colors are illusory because they don’t fit the prevailing paradigm — a great leap backward to the Greek atomists.