If a rainbow falls in the forest…

…and no one is there to see it, does it have any colors?

Ask a quantum physicist, and she’ll say yes and no at the same time! (Don’t try this, only quantum physicists can do it). It’s one of those paradoxes that philosophers, physicists and psychologists love to ponder. Not to mention certain artist/writers.


It’s all in your head

The world you think of as real—with green trees, blue sky, red and yellow flowers, or six-color rainbows—is a picture your brain creates for you, a reflection of objects in the world as seen through your own personal human eyes. The objects themselves have fixed characteristics—how their molecules are arranged—but they have no fixed appearance. It all depends on who’s doing the looking.


Are you a Super-Human Color Mutant?

I’ve always had trouble painting skies. Even way back in art school, I remember having discussions with fellow students about sky-color. “It’s not phalo blue,” I’d say. “…or ultramarine, or cerulean, or cobalt. There’s another color there! Don’t you see it?”

Blank looks.

Self portrait of young me in art school. Apparently I had a blank look, too. And big hair.











To this day, I’ve never been able to mix sky-color to my satisfaction. It seems there is something else up there…something more violet than green, more green than violet, but different than blue. Something completely un-mixable. I gave up on it long ago.

So, when I recently heard a woman on the radio say that she saw colors in the sky that looked ‘pinkish’, my ears perked up. Way up.

This woman was being tested for a genetic condition that scientists have long suspected in the female population—but have never proven, until quite recently. The very first known ‘tetrachromat’ has been finally been found. Apparently, there are women (sorry guys, this only happens on the X chromosome) that can see more colors than regular humans.

I knew it! Could I be a tetrachromat? Was it possible that all this time I’ve had Super-Powers I never even knew about? Imaginations ran wild. And, probably like every other woman who was listening to that same radio program, I immediately googled ‘tetrachromat’ and did an online color-confusion test.

Anyway, according to the internet, I’m just an ordinary human. And I still can’t mix sky-blue.


How We See the World  — In 3 Easy Steps

Step 1: Size Matters

The universe is filled with waves of light-energy, all essentially the same except for having different wave-lengths. They range from very long to incredibly short. They are all moving at the speed of light.


Step 2: Matter Matters

When the light waves (unpoetically known as electromagnetic radiation), encounter an object, they either pass through it, bounce off it, or are absorbed into it, depending on the size of the waves relative to the molecular structure of the object. The ones that bounce off are the ones that let us see the world.

Step 3: Cones Matter

Photo receptors called rods and cones in your retina become excited when struck by some of the light waves that reflect off objects and travel (still at the speed of light) straight into your eyeball. Your excited retina sends signals to your brain which interprets the signals and creates a picture. Result: your very own personal universe.


What you don’t see

But, human rods and cones detect only a fraction of the full spectrum of light energy that’s out there zipping around at the speed of light: what we call visible light. Drawn as a simplified linear graphic, the full spectrum of light-energy in the universe would look something like this, with the blank areas corresponding to wave-lengths we don’t see: gamma rays, radio waves, microwaves, infared and ultraviolet waves, and x-rays, to name a few.

The little rainbow strip is the only part of the spectrum that we can see…the rest is invisible to us.

But, there are many creatures that can see a much wider portion of the spectrum that we can—far more than even a tetrachromat. In fact, many birds, insects, fish and invertebrates can see into the ultraviolet and/or infared wavelengths. To them, the world must look a lot different than it does to us.



Red + Blue + Green = 1,000,000

Normal human eyes have three different types of color receptors (cones): red, green and blue, plus rods that detect light/dark levels. (A tetrachromat, by contrast, has 4 cones!). But, by mixing signals from only three color receptors, normal humans can perceive at least a million different colors. Our eyes and brains work together to create a palette of incredible richness.

But consider this: some butterflies have at least 5 or 6 color receptors, detecting colors into the ultraviolet range and with extra sensitivity to yellow and blue-green. Doing the math, it’s possible that butterflies live in a world with billions of colors. Of course, no one knows for certain what butterflies see— it could be that they need extra color receptors to make up for their simpler brains—but any way you look at it, a butterfly lives in a very differently-colored world than we do.

Tiger swallowtail butterfly on lupine, done for the Mountains to Sound project.













Oddly, the creature with the most complex eyesight by far is the mantis shrimp, which has 16 color receptors. What a world that must be!

uncredited photo of mantis shrimp from Planet Animal Zone.









Color and Art

There is more to our visual sense than light waves or the number of cones in our eyes. Awareness is a critical element to color perception. Scientists studying color vision believe that even though there are probably a number of tetrachromat-mutants walking among us that have the ability to see extra colors, they probably don’t realize they are any different than anyone else. It is possible to see colors without noticing them.

Most artists tend to be highly aware of color. As someone studying art, you learn very early to focus your awareness on colors you see with your eyes rather than your brain. In order to do this, we try to quiet our natural tendency for what scientists call ‘color constancy’ and artists call ‘local color’.

Color constancy is what Nature has given most creatures in the animal kingdom as an aid to survival—a way to simplify what they see so they fare better in the Eat or Be Eaten jungle out there. A poisonous bright red berry has to be perceived as bright red whether it is growing in the bright sunlight or the deep shade, where it’s red color may actually be barely visible.

But, as any art student knows, if you use bright red pigment to paint a bright red berry growing in shadow, you will fail miserably.

Artists who explore color have learned that the perception of color is enormously complicated. It might be simplest to describe what it is not: color perception is not static, concrete, or singular. It is the opposite of all those things…and then some. Much of the greatest art of the 20th century has been done by artists specializing in what color can do. One of my favorites happens to be my very own father, Richard Dahn:

Richard F. Dahn studied art at Yale University with Josef Albers, whose “Homage to the Square” series and other works pushed the boundaries of perception in the mid-20th century. Dahn’s work, like many of Albers’ students, grew out of the Albers tradition of intense colors, patterns and perceptual interplay.


Richard F. Dahn


Richard F. Dahn


Test your own ability to see with your eyes and not your brain and overcome color constancy:

The question: are A and B the same or different?



Answer: They are the same! (Don’t feel bad if you got it wrong. I had to print it out and cut apart the squares before I believed it myself!)


To hear the fascinating Radio Lab episode about color, tetrachromats, and more:


To learn more about the physics of light and the sense of sight:


To learn more about color vision, color blindness, and new medical breakthroughs:


Leave a comment or question! Do you think you might be a tetrachromat? Have you ever thought about what it would be like to see other wavelengths? Do you know other interesting facts or stories on this topic? Let us know!


11 thoughts on “If a rainbow falls in the forest…

  1. I do believe that i am much like this. I had considered that i was way different before, but one day i had been asked to paint a picture for someones special day…a face. In painting the face, my sister was watching and asked how i was choosing my colors. I asked her why. She asked why i was loading my brush with purples, greens, blues for skin tones. I asked her ” can you not see this color on the mans face?” She replied “no” . Now i understand why I’m so different! Thank you! 🙂

    • Thanks, Judi, I’m glad you found the post interesting. I think it is a fact that we all tend to perceive color differently. However, it is always good to get a professional opinion is you think that your vision may be “off” or significantly different from other peoples’. An eye doctor may be able to tell you whether your “seeing” of color is something normal or something extra-normal…or not. Might be a good idea to ask the next time you get a checkup! Meanwhile, have fun painting with those blues and purples!

  2. hello Denise Dahn,


    i have read several valid sites just tonight
    that make it clear that a small percentage of
    women (3 in 28 i think it was)
    and an even smaller percentage in
    men (1 in 12 fairly sure on this one)
    are tetrachromats

    all the descriptions sound like my life
    no color really looks the same to me
    sometimes i feel like i see
    the colors that make colors

    but irony
    despite many commercial & personal sites
    i’ve been coming across tonight
    i am as several research sites say:
    the 8%

    i am more and more sure i am a “tetra”
    and am wanting so badly to find some local testing
    in Greenville, South Carolina!

    my name is Jonathan
    i am male
    and i am quite apparently
    a tetrachromat

    it’s not unheard of
    in official research
    sure the random .com’s
    will generalize
    but i am not impossible
    nor improbable
    but i do feel a bit alone in this

    it’s kind of nice to think
    i have a better chance of meeting
    a lady with this blessing

    apparently this type of sight
    can be assessed estimatedly
    by asking inquiries such as
    how one perceives
    similar/dissimilar colors
    in routine
    and throughout life
    or even art

    realizing how obvious it could be
    to at least find a square-one
    is exciting ^_^
    e.g.: it could become a part of normal
    conversing to ask if someone is a “tetra”
    based on basic criteria
    (not unlike the DSM-IV)

    i’ve always had gifts in arts, memory, & naturopathy
    it gives me more hope to think
    i might be able to really use these gifts
    to their full potential
    being a savant
    i’ve always felt so… different
    well, the plot thickens!

    Peace *_* to all eyes
    Jonathan <3

  3. Pingback: Cosmic Sightseeing 2 | Denise Dahn, artist/writer

  4. This has been said numerous times and places, but tetrachromacy cannot be tested on the internet. Computer monitors use the three color system so they can only mimic trichromatic vision. If you suspect you’re a tetrachromat, talk to your eye doctor or a scientist. One possible test involves separating the spectrum with something like a prism and placing markers where you see a new color concept begin. Trichromats see the standard seven (Roy G. Biv) but tetrachromats see 10. This website http://www.colblindor.com/2007/04/17/deuteranopia-red-green-color-blindness/ compares a normal trichromat spectrum to a red-green colorblind one. It looks blue and yellow because we have a blue-yellow, a red-green, and a black-white processing channel and for whatever reason scientists think everything is being processed by the blue-yellow channel for them. If you find out you’re a tetrachromat, I’d be curious as to where you place the ten markers (if you take that particular test) and if the “normal” spectrum on that site looks so limiting to you that you intuit you must be using an additional channel.

    • Thanks for that helpful information, KJY! Next time I go to the eyedoctor, I’ll ask about it. It’s an interesting phenomena.

  5. Denise, this was fascinating! I’ve loved thinking about color perception since I was a kid. I would love to have been a tetrachromat, but that online test says no…still, I think I’m pretty sensitive to minor color variations. For instance, almost always when I look at the moon or other bright natural object, I see a red fringe on one side and a blue fringe on the other.

    I’ve also tried to paint the music I’m hearing, so perhaps I could claim to be a synaesthete. (The problem is that the music goes by so fast I can’t keep up!)

    How intriguing, wondering what the world must be like for animals who see so many additional colors. To spend an hour in the mind of a butterfly – wow.

    Thanks for a great post!

    • Thanks! It is fascinating…on the Radio Lab episode, they interviewed a doctor at the UW who is doing some really interesting research. They actually injected color cones into a monkey’s eye, giving it color sensitivity it had never had before! But, it took it some time for the monkey to notice the difference. And when it did, it got really excited.

  6. Sadly, no, I’m not, and I still struggle to paint what I see (but I’m learning). I’m never happy with my sky blues so I paint overcast days, which is what I see most of anyway. (Maybe that’s why I’m not observant about color.) I do, however, see my letters and words in colors, which is something else entirely, and good for nothing, except I used to be ridiculously good at jumbles.

    • Wow! You sound like you are a synesthete! (for those of you who’ve never heard of this, it’s a cross-sensory neurological condition. I had a piano teacher who ‘saw’ colors in every note she played.) I guess the form you have is not that uncommon. I think it sounds fascinating, actually. Have you ever tried ‘painting’ one of your writings? (for those of you who don’t know Murr, she is a writer, check out her very cool blog Murrmurrs) I’m imagining something like a pointilist painting, where every dot of color looks separate up close, but when you look at it from a distance, it makes a huge picture. What if your colored writing made some kind of picture that you didn’t even realize was there until you stood back and looked at it? Sounds like some good sci-fi!

  7. Well, I realized as soon as I hit ‘publish’ that I had mistakenly written ‘tetrachrome’, when the word is actually ‘tetrachromat’. The first one simply means four-colored, and the second one means a person with four color cones. I edited this version, but all you subscribers out there got the version with the error. Sorry!

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