There is something so elegantly beautiful about the circular chart. Color is a paradox to me. It is a thing we who have color vision simply assume as part of the physical world. It seems so empiric, so definite, yet it so subjective. We experience it as a quality of the objects around us yet it exists only in our brains. Just this morning the old question about a tree falling in a forest came up. If no one is there to hear it, is there any noise? The same question applies to color- is the field green if there is no one there to see it? The answer to both these questions is no. When the tree falls the event will send mechanical waves through the medium of the air, and an ear and brain working together interpret those waves as what we call sound if they each them, but that is in our heads, not in the forest.
When we "see," electromagnetic waves which are reflected off of a surface reach our eyes and are interpreted as a representational "vision." The sun shines upon the field, showering it with the remnants of energy waves that have not been blocked by the atmosphere. The sun, in it's seeming endless roiling of atomic explosion radiates on the fragile atmosphere which envelopes this tiny planet. The atmosphere fragments it into the glow of blue that we call sky. The energy that now has substance to interact with becomes visible as light as it energizes the air and irradiates the grass to give it the energy of life, and those wave lengths that the grass doesn't take in are reflected to our eyes and we experience a wave length, one that is not absorbed by the grass, and we have decided, as a group, a culture, to call that sensation green.
It seems to me that this agreement is rather like the "as if" approach to religion. Some of my friends in our theology discussion group will recognize what I am referring to. That we agree to participate "as if" it is all true. In the case of color, we agree to name it "green" as if we are all experiencing the same thing, but in fact all we know is that we each of us has that wavelength available to us if we are observing under the same conditions. It has passed through the air, been bounced off the grass, passed through more air, some glass perhaps, and now passes through our very probably yellowed cornea, thence to stimulate a now motley collection of much worn rods and cones and then the resulting stimulus winds it's way through the rather quirky maze of the individual brain to create that experience that we call green, which we treat as if it were identical for us all.
We can never know if the experience is the same for all of us- all we know is that when we see that wavelength we recognize it's sameness to the other occasions on which it is visible to us. I am wearing a sky blue sweater, it is the color of the sky, the egg of a robin. I say it is the color of the sky "Blue" and you say"oh yes! the color of the sky, like the egg of a robin, your sweater is that lovely, light, and slightly greenish blue." But really, beyond the fact that this sweater is showering you with the same wavelength as a clear sky on a cool summer morning, and so you make that pleasant association, the experience is completely within yourself, and you are profoundly isolated within your reactions to the wavelength of light, as I am within mine, and it is only the consistency of our individual experiences that enables us to shout across the gulf of sensual interpretation that separates us, and allows us to talk "As If" the field were green, and the tree crashes loudly, and the beauty of the world around us makes us one with creation.
We are dealing with, not the wavelengths that are in the grass, but those that are not in the grass. One could say that the grass is every color except green. It has rejected the greeness, thrown it back to us. This is another aspect of the paradox, that the color the thing is "is" exactly the color it "isn't." The grass gives our eyes "green" as the left over of it's feast on the sun's life giving energy. And we see it with pleasure.