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!