No,mthat is not clear at all. You cannot swap the colours so that the sky becomes green, or leaves become blue. The colours are there because of physics.OK, so there is there are the following types of red:
1. Certain frequencies of light.
2. The activation of certain structures in the eye.
3. Particular patterns of activations in the brain.
4. The first person experience that we get when those activations in the brain occur (which may very well just be 3 from a particular point of view).
5. The label that we put on things that are "red".
Clearly it is possible to swap the colours around by meddling with 1.
Again, I do not see how you can make any swapping here. The cones activate because they have the physical properties to react to those exact frequencies of light. You cannot use a cone sensitive to red light react on blue light.Likewise if you mucked around with the eye, you could presumably swap colours about. It's not as if L-cones activating for red and S-cones activating for blue is "the correct" representation of reality, is it?
Finally, I do not see the point of swapping at all: those data structures that have been connected with red light are also connected with "heat", and "stop (in stop lights)". While the choice of red for "stop" is decided by humans, and is arbitrary, the same is not the case for "heat". If you were able to swap green and red in the mind, the sight of glowing coals would no longer be red, and you would no longer have the connection to heat.Same with the patterns of activation in the brain for red. Let's swap blue and red. It would be confusing if it happened, but it wouldn't be any more correct or wrong than the normal mapping. No?
In other words, the data structures in our heads do have a connection to the physical world around us, so they are not arbitrary. Besides, the data structures have been built by a learning process, which again does not make them swappable.
Piggy's example of colour-blind people experiencing different colours is right and wrong at the same time. It is true that because of a lack of appropriate cones in their eyes, these people have different physical input, but the physical colours are unchanged, and R-G people will still have data structures for red green, even if they look more or less the same to their eyes. These data structures have been built by experience: as children they have been told what is red, and what is green, and they make the same associations with the colours (such as "ripe", and "unripe", or "go" and "stop") as everybody else, but the colours are just more difficult to tell apart for them.
Some women apparently are quadrochromatical, which means that they can see a fourth colour. We trichromatical beings cannot imagine what it is like to see four colours. As far as I understand, the fourth colour is in the green area of light, and quite close to the 'old' green. Since our world is dominated by trichromaticals, the quadrochromaticals will be taught the same colours as the trichromaticals, and make the same associations, and they might never realise that they can see an extra colour. However, they will be able to distinguish green nuances far better than we can.
So how is it to experience 'red', and will all people have the same or a different experience? My answer is that most of the data structures will be exactly the same, such as the connection to red apples of glowing coals, and that we might never know what mental picture we have internally of a colour, and if they would look the same. My first guess would be that no two people would 'see' a colour in the same way, but I am sure they will all call the colours the same. However, in this very thread, a link was posted to a paper that claimed to have found a smart way to determine if everybody saw colours in the same way, and that the answer was that we do. I do not have the time to dig up the link now, but it is quite a long time since it was brought here in this thread.
If the paper is right, it would seem counterintuitive to me, and it would imply that our inner colours are much less arbitrary than we think. For a computer model, it would imply more hardware, or hard-coded code, and less software.