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What if two people call a color the same name but their eyes see different colors? Is it proven that that's not possible?
Answer 1:

Great question! What you've described is entirely possible! In fact, it happens all of the time. You're quite right that there are physiological differences in people's eyes. The cells in our retina, called photo receptors, are generally sensitive to what we call blue, green and red colors. It is actually more accurate to say that these photo receptors are generally sensitive to short, medium and long wavelengths because, as you suggest, what one person calls "red" may have different physical properties than what another person calls "red".

The reason for this is that photoreceptors vary in the wavelengths at which they are most sensitive. For example, one person may have "red" photoreceptors, or "long-wavelength cones", that are most sensitive to wavelengths of light around 564 nanometers. Another person may have long-wavelength cones most sensitive at 568 nanometers. This may seem like it isn't much of a difference. However, this slight shift in photoreceptor peak sensitivity can make all the difference in the world when it comes to perceiving colors as "red" versus "orange", or other colors.

So, as you say, different people may color the same name even though they are seeing different colors (i.e., perceiving light with different physical properties). And, people may perceive colors of the same physical properties and call them something different! That is, if you shined light with certain physical properties in my eye, then shined the same light in your eye, it's very likely that we would say they were different colors. That's because our photoreceptors are different. It could also be that you and I have learned to call the same thing by different names.

Remember, the physical properties of light may be objective (measurable) but the names we give the light we see (e.g., "color") are entirely subjective. If your parents taught you to call apples "red" and my parents taught me to call apples "blue" then, when looking at the same apple, we would label them different color!

Now, think about this: There are entire industries that try to reproduce color in ways that look good to us. Take, for example, television. When images of real objects (say, apples) are reproduced on television, the light that is used to make these images is artificial. Televisions, instead of using the full spectrum of light, use "phosphors" to produce visual images. These phosphors, generally called blue green and red "guns", are supposed to match the spectral sensitivities of our photoreceptors (cones). But, as you pointed out, people perceive things differently.

How can we make televisions so that people perceive the images exactly the same way? In fact, is it even possible? If you really want to stretch your brain, check out the research by David Brainard
human vision
who studies human vision, machine vision and computational modeling of visual processing. He's worked on this stuff for a long time. But, watch out! This is tricky stuff!!!

Answer 2:

This is actually very common. Many people see the same color differently. For example: my son is not blind to all colors, but he cannot distinguish them very well. He sees brown and green as the same, for example. We only found this out when, in second grade, he would get colors "wrong" on tests, and we took him to an eye doctor, who confirmed that he did not see colors like everyone else. But I also tested him with a rainbow of colors from sunlight passing through a crystal, and making a rainbow on the wall. He claimed he could "see" well into the infra red - beyond the end of the red end of the spectrum, well beyond where I could see.

So, people actually do see in different ways. The "colors" are named as they are because that is what MOST people agree that they see. What we call colors are actually vibrations of an electromagnetic field at different frequencies that are detected by our eyes, and interpreted by our brains. The "scientific" definitions of colors are not the same as the"psychological" definitions.

Eye doctors have tests for this, so people can find out if they "see" the same as the "standard."

Answer 3:

Good question. It shows that you know the difference between the world and our perception of the world. Our perception is how we see the world and it is influenced by who we are and by our senses.

We all learn to give specific names to specific colors when we are very young. But that doesn't guarantee that we see the same thing. Maybe I see a particular shade of gray when I look at a green object. I will learn to call that shade of green "gray" and may never know that it looks different to me than it looks to other people.

If someone asks me if I can see green, I'll say "sure" because I think I'm seeing what everyone else sees when they look at a green object. That's why you need special tests to tell whether someone is colorblind. Check out the tests on this page:
color blind

Notice that the circles are all different shades: some are light and some are dark. That is because even a person who can't see color can tell whether a shade is darker or lighter. What part of our eyes let us see color? Why are nocturnal animals usually colorblind?

Answer 4:

The simple answer to this question is that everyone's eyes see the same colors, but we don't know if their brain's are interpreting that in the same way. To answer this we must first understand what colors are. When you see colors, the tissue of your eye is telling your brain that it has been hit by a certain kind of energy. This type of energy, which we call light, is actually a form of radiation. This radiation comes in many other forms that you have heard of: microwaves, radio, UV (ultraviolet), infrared. These are all made of the same thing: photons.

Most people don't know this, but the difference between red light and green light is much like the difference between red light and microwaves or radio waves. Photons travel through the universe in a wave-shaped pattern, just like the waves on the beach. When you go to the beach, you see waves hitting the shore. The first thing you notice is how big the waves are. The second thing you notice is how often they crash on the shore. These two characteristics define whether the photons hitting you are radio waves (these are often large waves that don't crash very hard) or x-rays (tiny waves that come really fast).

Colors are defined as photons which have a very specific "wavelength", which is a number describing how large and how fast the waves of photons are hitting the detector (your eye). If the wavelength is 700 the light is red, if it is 450 the light is blue. So we know for sure that the light that you call red and the light that I call red are defined by the wavelength of the energy hitting our eyes. So what does our brain do with this? Do I see red the same way that you do? The answer is not known.

We do know that many men have a genetic difference which causes them to be colorblind. For many colorblind people, reds and greens seem like shades of grey. In other words, they can't distinguish dark red from dark grey. It may be that when you see red the color in your brain is more like the one that I call purple. This is hard to determine because it is based on how your brain works, and we know very little about how the brain works. But most people can see the full range of light wavelengths and see how they differ. Most people can't see x-rays or microwaves or radio waves because their eyes are not adapted to detect those kinds of radiation. Good luck!

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