No, it is the production of specific colors. Different wavelengths trickle down through the visual system to make differently activated neuronal populations, which is color.
You see red instead of green because the red population - the population that's active when a red wavelength is presented; the population that differentiated itself over time by repeated presentation (at least 20 weeks, if the linked paper is accurate) - is active, and not the green population. That's it. We're done. There's no next step. That is the color, that is seeing the color, that is the experience of seeing the color, that is however many nested layers of homunculous special pleading you want to wrap around the damned thing to convince yourself that you're more than that. You're not. This is where it all happens, and there is no magic bean here.
There's no magic bean anywhere. Nobody here believes in any magic bean. Can you please, at last, stop with that nonsense? Thank you.
Yes, different wavelengths of light trigger different sorts of neural reactions which result in the experience of different colors.
But you still have not answered -- nor, apparently, understood -- the question.
There is, at present, no physics, no calculus, no theory of any kind which explains why the specific colors are what they are.
If we shine a light in a person's eye (observer A) and have another person (observer B) observing the first person's brain activity, we have two sets of observations.
Observer B can see how the light triggers neural activity. And we have physical theories to account for that. We also have physical theories to account for any response such as squinting or reflexive muscle movement.
That's no problem.
But when we do this repeatedly, and with different wavelengths of light, we end up with 2 sets of observations which end up being very tightly correlated.
Let's say we try it with 6 different wavelengths, W-1 through W-6.
Observer B records that the brain has neural responses which vary regularly, let's call them N-1 through N-6. These are related in many ways -- all going thru the visual cortex, for example, but they're not identical, and their variance is perfectly regular.
And explaining this correspondence is no problem, given our current understanding of physics, chemistry, and biology. We know
why N-1 is always the response to W-1, and N-2 is always the response to W-2, and so forth.
The problem to be solved, however, occurs when we try to explain the observations of observer B with the observations of observer A.
When observer B records that the brain is performing N-1 through N-6, observer A consistently reports an entirely different set of observations of the resulting phenomenology, P-1 to P-6, which in this case happen to consist of colors.
The correspondence is just as tight and consistent as with the W-to-N observations.
But unlike the W-to-N observations we have no theory to explain
why P-1 to P-6 are arranged in that pattern, and not some other pattern.
We know that they
are, but we can't explain
why.
For that matter, we can't explain why it's that particular set at all. Why is it not instead P-47 through P-52, which could be colors or sounds or smells or any other bits of the phenomenological palette?
We can't find an explanation in the Ws, clearly, because that's just backing up the correspondence a step further, which doesn't help.
Nobody studying the brain believes that this correspondence is the result of magic (which is why your "magic bean" nonsense is just silly).
It's simply two sets of observations which are tightly correlated and for which we currently have no theory, or even the basis of a theory, to explain the correlation.
And it's not enough to say, "Well, it just
is". We
know it just is, but
why?
It's like when Newton discovered that gravity decreases in proportion with the square of the distance between two objects. After Newton, we could say, "That's just what gravity
is, it's an attractive force that weakens in proportion with the square of the distance."
But that observation doesn't explain
why that value should be what it is, and not some other value, such as the raw distance, or the cube of the distance.
So far, our Einstein of consciousness has not appeared to explain
why N-1 is correlated with P-1, and not P-24, or for that matter no P at all!
In everyday terms, we don't understand
why a normal human brain sees a green light on the bottom of a stoplight and a red light on top, and not the other way around.
We know that it is the case.
The question is why.