Color inversion
I first heard this conundrum was about five years old:
what if I see red the way you see green, and you see red the way I see green.
How can we be sure that the experience of a color is the same for all people? What is the nature of experiencing a particular color in the first place?
Colors are a social construct learned from your parents and from your community.
Your perception of a color is formed from your experience with the color. To the extent that our experiences with a color are the same, then our perceptions will be the same.
Spectra
We start by understanding that there is a spectrum of light that enters the eye, but from there it produces a perception, which is possibly entirely different for different people. But this question also illustrates a fallacy of sorts about perception and particularly about color.
Understand first that there are more colors than exist in the rainbow. The color 'magenta' does not appear in the rainbow. How can this be? The colors we experience are in a roughly three dimensional space defined by the frequencies of the three different cone photoreceptors in the retina of the eye. I say roughly three dimensional because these are not entirely independent -- light at any given frequency will trigger more than one cone. But it is still the ratios of the intensity at the three different kinds of cones that define the basic sense, however there is more to it to see a color.
The spectrum draws a roughly linear line through the three d space of color. The spectrum traces through most of the main colors, it is appears that all colors are on the spectrum, but if you really look closely there are lots and lots of colors that can not actually be found on the spectrum. Take any color tab from the paint store, and the carefully walk through the spectrum and try to find the exact color, and most likely won't, because the pure colors of the spectrum are quite limited.
The main message here is that color is certainly not a point on the spectrum. The points on the spectrum to map into colors, but there are many many more colors than that. So something more than a spectrum is going on.
Social Construct
There’s plenty of evidence to show that color is a social construct. We learn to distinguish particular colors and we give them names. According to whatever language you speak. Different cultures have different numbers of distinct colors. For example, in English, we distinguish between red and pink as being two different colors -- and honestly if I thikn carefully about it pink seems to me to be a color different from simply being light red. English speakers don’t distinguish between green and light green as being different colors, but Russians do; there are two words for green in Russian and one means light green as a color distinct from dark green, and they see them as distinct colors.
Culture will indicate colors that are important to be distinguished. For example, there’s a tribe in Africa, which has two colors, both of which look to be a spring green to me, but to them they are two entirely different colors. When I look at them closely I can barely tell them apart, but apparently these are colors of leaves, which is very important for this tribe to distinguish it.
Color Perception
What does it really mean to perceive a color? When you look at something red, it seems to have redness about it. There appears to be something that it is like to be red.
We know that color is not a point on the spectrum, but still if I point at something that is red, unless you’re colorblind, you will agree that it is red. This says nothing about whether we’re having the same internal experience or not.
Your actual perception of color is not innate, but instead it is learned. We know this because while everybody within a particular culture can agree on what color is what, different cultures have different numbers of colors. It’s pretty clear that people learn from their parents and their peers what is and is not a distinct color. This means that colors are not universal and they’re not genetically inherited either. The perception of a particular color is learned from your environment and your culture.
Same Culture
We might conclude that different people from different cultures will have different perceptions for different combinations of light spectrum. But what about people in the same culture? How can I be sure that your perception of red is pretty much the same thing as my perception of red?
Since we learned from our culture environment, if we grow up in the same culture in the same environment, our experiences will be the same for the different color spectra. We will have the same sorts of memories for the same sorts of colors.
Memories
Memory is a way of actually re-experiencing the event that you remember. If you have a memory of stubbing your toe, then, remembering that is a bit like re-experiencing the toe being stubbed. When you recognize something, it is a kind of remembering. When you recognize it person's face you do, in some important ways, relive experiences that you had had with that person.
All of this is true of the perception of color. When you recognize the color red, you are in a very real way re-experiencing red things from your past. The color red might allow you to re-experience a sunset, a campfire, blood, and other red things. Your experience of read, as a property is simply the memory of a large number of red things mixed together.
If you and I grow up in the same culture, and in the same region, then our experience of red things will be largely the same. Sunsets are red. Fire is red. Tomatoes and other fruit can be red. Blood is red. And so on: we all come into contact with a certain variety of objects that are red, and our experience with those objects are what we associate with red.
Thus, the sight of anything red, I am actually reliving the sight of a sunset, and blood, and a glowing heating element. Everything associated with red come flooding back in when we see something red. We are not confused about this; it is not the case that every time I see something red I think it is a tomato. But when I see something red, it is somehow associated with a tomato. And everything else that I have every seen that is red.
Common Experience give Common Quale
That is how I can say with confidence that people in the same culture of the same reason generally experience a color of the same way. People who grow up in an entirely different culture in a different part of the world may in fact have a different perception of the color.
It is very unlikely (probably impossible) for your experience of green to be identical to my experience of the red. for that to happen, you would have had to have seen green sunsets, green fire, green blood, and green ripe tomatoes. (Ok there are green tomatoes but you know what I mean, right?) Your qualia is tied directly to the memories of things that have been red, and it is nothing more than that. Because of differences in our experiences we might have small differences in how we perceive red, but it is flat out impossible for your experience of green to match up will my experience of red.
Inverted World
As long as we’re speculating, we might envision a color in an inverted world. Alex in world, one sees things color the way they are on earth. Bernard lives on the planet, where blood is green, sunsets are green, and fire is green. Similarly on Bernard's planet leafy plants have bright red leaves. Everything that is red on earth is green for Bernard and everything that is green on earth is red for Bernard. In this situation it’s entirely possible for Bernard to experience green in exactly the way that Alex experience is red.
But inverted worlds simply can't happen. This is one of those hypothetical situations which doesn’t happen in reality because it is logically excluded. Sunsets are red because of the way atmosphere works. Plants are green because of the way photosynthesis works.
Your perception of a color is formed from your experience with the color. To the extent that our experiences with a color are the same, then our perceptions will be the same.
Root Fallacy
I hope this explains how color inversion really can’t happen with people that are growing up on the same planet. Yes, it’s true that the actual perception of the color red may be very different for someone who grew up in Alaska from someone who grew up in tropics. There are differences in the way that color is perceived. But there is no chance that I will perceive one color exactly the way that you perceive a different color.
Asking this question exposes the fallacy of thinking that there might be some sort of preordained way that a particular color is to be perceived. It’s like as if inside of brains, there are fewer pathways that mean red pathways that mean green, and it might be possible that one person is another person Another. It’s a fun question to ask. But it assumes pre-ordained innate color perception experiences. There’s no evidence that such a thing exists. There’s a lot of evidence that color perception is learned from your environment and culture. Because it’s learned, two people in similar environments will, by definition of similar experiences, and similar perceptions will be built from those experiences.
Colors are a social construct learned from your parents and from your community.