What Are Colors?

Look at this picture.  Can you read the number on the left?  Or do the two circles look the exact same to you?

If they look the same, then, surprise (you probably already know this): you might be colorblind!

Colorblindness (or 'color vision deficiency') apparently affects roughly 1 in 12 men and 1 in 255 women. Why does it affect men so much more? Because:

males only have one X chromosome (XY, with the Y chromosome carrying altogether different genes than the X chromosome), and females have two (XX); if a woman inherits a normal X chromosome in addition to the one that carries the mutation, she will not display the mutation. Men do not have a second X chromosome to override the chromosome that carries the mutation.

(There's a lot more to colorblindness and there are many different kinds; I'll discuss that later).

I recently listened to a fascinating podcast on color (listen here!) and learned a ton of stuff, much of which I'm recounting here (with many additions and thoughts by me).

So, color. Yeah, what a concept. Have you ever noticed how strange an attribute of things it really is?  For those of us who are not colorblind, it is one of the first things we notice about an object.  The apple is red.  The sky is blue.  The grass is green.  However, is color an innate part of an object?  And by that I don't mean: "Is grass always green?"  What I mean is: "When grass is green, is that green something concocted in our minds, or is it something about the grass, external from ourselves?"

The answer is quite simply (or difficultly), both.

What?

Let me explain.  First, here's why it's something innate.  When grass is green, it is because it, externally of us, reflects green light.  When the white-colored light of the sun comes down, it is actually a combination of all the colors of the rainbow (which are all at different wavelengths...remember fifth grade science and prisms?).  A green object, such as grass, will absorb all of that light except for green.

Here's the general concept

Here's how green works in particular

Of course, the reasonable question to ask is why does it reflect green?  Is that arbitrary?  What is happening below the surface that causes it to do that?

The answer, in the case of grass, is chlorophyll.  With other objects, it is based on whatever their chemical makeup is.  That's because everything depends on the molecules within an object, and, more specifically, the electrons.  Here's how it works (h/t):

Similar to a tuning fork or even a musical instrument, the electrons of atoms have a natural frequency at which they tend to vibrate. When a light wave with that same natural frequency impinges upon an atom, then the electrons of that atom will be set into vibrational motion....If a light wave of a given frequency strikes a material with electrons having the same vibrational frequencies, then those electrons will absorb the energy of the light wave and transform it into vibrational motion. During its vibration, the electrons interact with neighboring atoms in such a manner as to convert its vibrational energy into thermal energy. Subsequently, the light wave with that given frequency is absorbed by the object, never again to be released in the form of light. So the selective absorption of light by a particular material occurs because the selected frequency of the light wave matches the frequency at which electrons in the atoms of that material vibrate. Since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies of visible light.

Got that?  So, basically, some light (blue and red in the case of chlorophyll and grass) is absorbed because the electrons within the molecules of an object are vibrating at the same frequency as the lightwaves.  Huh.

So, in a sense, that answers my original question.  Green grass is inherently, innately green.

Well, not exactly.  What's more accurate to say is that grass reflects light with wavelengths that fall roughly between 430 and 660 nm.  So, that's innate.  What is perceived is a different matter.  When that light is reflected to our eyes, it hits the rods and cones (specialized photoreceptor cells).  Those cells react to any light between the wavelengths of roughly 390 to 750nm.  Because the reflected light from our example is within that spectrum, the signal transferred to our brain from the cells produces the sensation that we are seeing something that we identify as a color (green in our grass example).

So, colors are both innate and perceived.

What do other organisms perceive?  What does my dog see?

Wow, that's a great question!  I remember thinking this goofy commercial was totally hilarious when I was a kid:


Of course, now I know that it not only isn't hilarious, but it's incorrect!
When we say that our pets are colorblind, our mind immediately thinks that they must only see the world in black and white.  Their entire existence is like one long episode of Leave it to Beaver.  Well, that's totally wrong!
Dogs (and cats), it's true, are colorblind.  However, they are no more colorblind than any of you who couldn't read the number at the top.  Well, kind of.
Dogs and cats can see roughly the equivalent of a red-green colorblind person, meaning that the colors red and green basically don't exist for them.  Everything on that end of the spectrum looks like a bunch of yellow.  They can, however, also see blues and purples, though less vibrantly than humans (their brightness receptors are not as good as ours).  Interestingly, they can also see a little more purple than we can (closer to the ultraviolet scale).

All of this is because dogs are dichromats, meaning that they have two types of cone cells in their eyes.  I believe that they are missing the green receptor, which causes both red and green to appear as yellow (similar to anyone with red-green colorblindness).  Cats are the same way.

That commercial, then?  Poor Duke wouldn't be able to see the red layer on the outside, but he'd certainly be able to tell the difference between the white layer, the yellow layer, and the blue layer.  Duke is just being modest.  But keep that in mind the next time you wear your red aloha shirt.

Research on other animals has found some interesting results.  Most mammals are thought to be dichromats, with some notable exceptions.  Marsupials have three types of cones ("trichromats"), like humans, so are believed to be able to see what we see.  Primates, save a species called the owl monkey, are also generally trichromats (with a few dichromats in the mix).  Many marine mammals, including pinnipeds (seals, sea lions, walruses) and cetaceans (whales and dolphins) are monochromats, meaning that they can only distinguish (at most) one color.
It gets crazy when you get outside of our happy mammal class.  Reptiles and amphibians all have at least four (some have five) types of cones, meaning that they probably see additional colors than the ones we can process (their brains are still the size of peas, so we win that battle).  Many birds have extra cones, and even some fish have more highly developed color receptors than our own.
Beyond that, within the invertebrates, most have color vision.  Bees are trichromats, but they can't see red.  Instead, they can see well into the ultraviolet spectrum.  Butterflies have six types of cones, and it is believed that they can see many more subtle colors than we are able to between green and blue wavelengths.  But the winner, with by far the most cones?  This guy:

"Lookin' good, baby."

The mantis shrimp.  It's eaten as sushi, it has been known to break out of aquariums, and it mates for life.  It also has twelve types of cones.  That's double anything else we know of in the animal kingdom.
Colors and People

Black, white, red, green, yellow, blue.

In studies of language and literature, it has been found that this is almost always the order that colors are identified.  When it is different, one thing holds: within the color spectrum (outside of black and white), red is always identified first, blue is always last.

In fact, according to the podcast I referenced, of ancient cultures, only Egyptians had a word for blue.*  Even the vaunted Homer, (mythical?) author of the Iliad and Odyssey never mentions the color blue.  He speaks of black and white frequently, red almost as frequently, yellow and green a bit less, and purple a bit less.  However, there is no apparent concept of blue.  This led William Gladstone, Prime Minister of the United Kingdom and major Homerphile, to posit that Homer was colorblind.  Not sure if Gladstone realized that, according to legend, Homer was, well, blind.

"Oops."

Now, that may not be true.  The legend of Homer being blind may very well come from the fact that his name, in some ancient dialects, means "one who is forced to follow" or "blind."  But, there's also legend of him being taken as a hostage, which is another meaning of the word.  So who knows?

But that brings us back to earlier question.  Why did it take us so long to identify blue, when it was sitting right there in front of our faces?

Well, posit some scientists, we may just not have noticed it.  As I noted many moons ago in another post, blue is incredibly rare in nature.  Outside of the sky (and therefore water as well), blue just doesn't really appear.  Even the blue flowers we have were mostly selectively bred for just that; they aren't naturally occurring.

So, as mankind began drawing things and writing things, we were able to easily get our hands on black (charcoal), white (chalk), and red (blood/dirt/clay/plants).  Brown, yellow and green are also easy to get.  Once you've developed wine, purple is yours, too.  But without the lapis lazuli stone, you just can't really make something blue.**

"Wait, wait, wait!" you say.  "The sky is a pretty big thing.  The ocean is a pretty big thing.  How could we not even notice it?"

Good question!  Ask the Himba tribe of Namibia.  The Himba don't distinguish blue.  To the Western mind, that's hard to imagine.  But watch this video, and see for yourself:



It's totally plausible that for thousands of years, we simply didn't notice the color of the sky.  It was part of the infinite void of the air.  When it was dark, we recognized the darkness.  When it was light, we recognized it as light.

Isn't that weird?

In Conclusion

Color is fascinating.  Be thankful that you can see any color at all, let alone the estimated one million colors that the average person can distinguish.

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* There is a legitimate debate about whether the Bible discusses blue. It's not a question within the New Testament, by which time blue, while still rare, was used throughout the Roman Empire (ὑακίνθινος - "hyakinthinos" - is the word in the New Testament, usually translated as blue, but also often referring to purple).  "Tekeleth" is the Hebrew word in the Old Testament, usually translated as blue.  However, there is debate over whether it refers to blue as we understand it or violet, because it is used as both within different Hebrew writings. 
** Interestingly, because blue is not a naturally occurring color of foods humans generally eat, we associated it (often subconsciously) with bad or spoiled food. Restauranteurs are often encouraged to limit their use of blues, because so many people have blue-food-revulsion.