When I was a kid, I used to wonder if everyone saw the world in the same way. We can all look at the same grass, but maybe the color I called green showed up in my brain as the color my friend called blue. Maybe all of our colors were shifted around to the point where all the colors were accounted for, but how we perceived them was shuffled up. I thought it would be remarkably exciting, and hoped that I could see the world through someone else’s brain to see if, in fact, this was true.


My eight year old self would be bitterly disappointed technology today has not progressed far enough to make that wish a reality. At the time, we had to settle the debate by another manner – asking an adult, a source of concrete and immutable knowledge. The answer I was given was that everyone sees the same colors of course (although why this was so obvious was never really clear) and if they didn’t it wouldn’t matter much since we couldn’t tell. Color was “real” – bits of light had a color (later I found out we could call it the wavelength of a photon), it hit our eyes, and our brains converted it to a beautiful image.

The only problem is that this is wrong.

Color as Wavelength

Well, alright. Before you get upset, it isn’t completely wrong. We were all taught about Sir Isaac Newton who discovered that a glass prism can split white light apart into its constituent colors.


While we consider this rather trivial today, at the time you’d be laughed out of the room if you suggested this somehow illustrated a fundamental property of light and color. The popular theory of the day was that color was a mixture of light and dark, and that prisms simply colored light. Color went from bright red (white light with the smallest amount of “dark” added) to dark blue (white light with the most amount of “dark” added before it turned black).

Newton showed this to be incorrect. We now know that light is made up of tiny particles called photons, and these photons have something called “wavelength” that seems to correspond to color. Visible light is made up of a spectrum, a huge number of photons each with a different wavelength our eyes can see. When combined, we see it as white light.


So this appears to resolve my childhood debate. Light of a single wavelength (like that produced by a laser) corresponds to a single “real” color. The brain just translates wavelengths into colors somehow, and that is that. There’s just one problem.

We’re missing a color!

Color as Experience

To find out just what we’re missing, we have to consider how we can combine colors. For instance, you learned some basic color mixing rules as a kid. In this case, let’s use additive color mixing since we’re mixing light.


Let’s find two colors on the spectrum line, and then we can estimate the final color they’ll produce when you mix them by finding the midpoint.

Red and green make yellow.


Green and blue make turquoise.


Red and blue make…


Green? What? That doesn’t seem to make any sense! Red and violet make pink! But where is pink in our spectrum? It’s not violet, it’s not red – it seems like it should be simultaneously above and below our spectrum. But it’s not on the spectrum at all!

So we’re forced to realize a very interesting conclusion. The wavelength of a photon certainly reflects a color – but we cannot produce every color the human eye sees by a single photon of a specific wavelength. There is no such thing as a pink laser – two lasers must be mixed to produce that color. There are “real” colors (we call them pure spectral or monochromatic colors) and “unreal” colors that only exist in the brain.

A Color Map

So what are the rules for creating these “unreal” colors from the very real photons that hit your eye? Well, in the 1920s W. David Wright and John Guild both conducted experiments designed to map how the brain mixed monochomatic light into the millions of colors we experience everyday. They set up a split screen – on one side, they projected a “test” color. On the other side, the subject could mix together three primary colors produced by projectors to match the test color. After a lot of test subjects and a lot of test colors, eventually the CIE 1931 color space was produced.


I consider this to be a map of the abstractions of the human brain. On the curved border we can see numbers, which correspond to the wavelengths in the spectrum we saw earlier. We can imagine the spectrum bent around the outside of this map – representing “real” colors. The inside represents all the colors our brain produces by mixing – the “unreal” colors.

So let’s try this again – with a map of the brain instead of a map of photon wavelengths. Red and green make yellow.


Green and blue make turquoise.


Blue and red make…


Pink! Finally! Note that pink is not on the curved line representing monochromatic colors. It is purely a construction of your brain – not reflective of the wavelength of any one photon.

Is Color Real?

So is color real? Well, photons with specific wavelengths seem to correspond to specific colors. But the interior of the CIE 1931 color space is a representation of the a most ridiculously abstract concept, labels that aren’t even labels, something our brain experiences and calculates from averaged photon wavelengths. It is an example of what philosophers call qualia – a subjective quality of consciousness.

I later learned that my childhood argument was a version of the inverted spectrum argument first proposed by John Locke, and that the “adult” perspective of everyone seeing the same colors (and it not really mattering if they didn’t) was argued by the philosopher Daniel Dennett.

I have come no closer to resolving my question from long ago of “individual spectrums” – but for the future, I vow to pay more attention to the idle questions of children.

127 thoughts on “Color and Reality

  1. also consider then that due to the ‘colours’ our brains ‘see’ we might actually all have the same favorate colour, tho its actual mesurable wavelength being the different.

    however an argument against this might be how we describe how a colour makes us feel, most noticable with temprature, red being warm and blue being cold.

  2. I’ve always wondered the same thing about individual spectra, and this is the first I’ve heard of the idea being explored. Thanks for the informative post!

    • i am not sure girls all over the world naturally “like pink”, what you are seeing is western (specificly american) cultural imposition, because dont forget pink used to be a boys color

  3. Ok, so what am picking up is that color is percieved, and about Pink, Thank you, now where is black in the spectrum, what wavelength of photons corespond to black?, and if it does not appear in the spectrum, does this therefore mean that black is not a color? How do we then see black objects? i thnk we should keep in mind that black absorbs all the wavelengths of light and reflects none back to the eye.

    • Hi Thuto,

      I think of black as the absence of color – the “canvas” on which our mind draws the other colors we perceive. Up to you and your semantics if you want to consider it a color or not!

  4. Interesting! I long am pondering about a related question, not having to do with colour but with geometry, as it is perceived by human beings. I think we are (almost) all able from young adults on to tell what the definition of a square is and how to recognize a square object with almost 100% certainty. The light we see in our eyes is guided by nerves to our brain. There this information is somehow mapped to produce an image to our consiousness. This image represents reality to the individual, beside colour also shape. Two persons looking at the same square agree that it is a square. Both recognize the same characteristics of that square, or, the mapping in both their brains produces the same geometrical info to their consiousness. How can the brain be sure that the image of reality presented to our consiousness is the actual geometrical situation of reality? For example, it should be easy to apply a conformal mapping to this image and present this to our conciousness. A distorted image would be the result but in that case this person should tell that the actual square is not at all a square but some weird twisted shape.

    Try to create a model of the eyes using optical fibers that guide the light as in nerves and project these dots of light to a screeen such that the original image is seen again. This already is quite difficult…

  5. I had the exact same question in my mind.. what i viewed as red.. would someone else view as blue :d.. but i could never ever make anyone understand what i was trying to state.. but for me it was not just colors. it was everything and anything that we take as inputs.. smell, touch, taste.. everything… at some level it seems very stupid.. but then again.. if you really understand the question.. its really something.. m glad to have stumbled on this page.. !! waiting to hear back from you! 🙂

  6. This was one of the questions I asked myself often when I was little as well. I thought it would explain well why I liked certain combinations of colours and others did not. I’ve discussed it with many friends (usually after a few drinks) and I have found quite a few others who have wondered the same thing. As for Albert and his geometrical take I must admit I don’t have as easy a time picturing it and while I don’t think it fits as well as the colour theory it is an interesting idea to think about.

  7. Wow! I am so excited to stumble upon this post!! I have had some pretty interesting conversations with my dear friend on this same subject! We have been discussing Fibonacci number, color wavelength, and sound pitch, when combined, create energy. It seems that with your post on colors, Albert’s comment on geometry, and our discussions on the combined subjects as we perceive them may make for very enlightening conversation! I look forward to your responses!

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