What is color? (and how does it work)

I was talking a friend the other day about color and it dawned on me that most people don’t understand how color works. Or even what color really is.

What is light? Light is a wave of electromagnetic disturbance. Okay, that didn’t help so lets ignore that for a second (and also ignore particle duality and all that physics oogabooga).

Let’s liken light to a sound wave for a moment. You strike two sticks together (a mechanical disturbance) and a wave of sound is emitted from the sticks. The wave travels outward through the air and eventually reaches your ears where the sound is detected and experienced.

If you press a piano key, a hammer strikes a piece of wire which vibrates. This vibration provides a mechanical disturbance. The piano has a collection of wires of different sizes and tensions so that they vibrate at different frequencies. Lower frequencies where the rate of vibration is slower produce lower notes. And of course faster frequencies correspond to higher notes.

Of course there is sound with a vibration speed too slow or too fast for us to hear because our ears have limitations. Apparently dogs can hear things we can’t because their ears work better for higher frequencies (higher notes).

Okay, now that we understand that light is a disturbance like sound and that it has a frequency like sound, we can take a look at color.

Color is essentially the frequency of light. Lower frequencies produce the reds and higher frequencies produce the blues in our experience.

So reds are like low notes and the high notes are blues. (To reference the sound analogy).

So there is light we can’t see because the frequency is too low (infra red for example). Light we can’t see because the frequency is too high as well (ultraviolet for example).

So a given piece of light has a specific frequency. What sort of frequencies are we talking about? Green light is around 540 THz. That’s 540 Tera Hertz or  540,000,000,000,000 vibrations per second. If we compare that to sound, an A note (somewhere around middle C) is 440 Hz or 440 vibrations per second. Of course you can have light that’s around 440 Hz too. The catch is that your eyes can’t see it but it exists. In fact, I think it’s referred to as radio waves. (Bet ya didn’t know that radio is the same fabric as color….)

There are two ways of talking about the frequency of a piece of light. One is known as frequency and the other is wavelength. In a nutshell, as frequency increases, wavelength decreases (in fact one is the inverse of the other). If that’s too much of a mouthful, consider a highway where the cars drive 100km/h. If you are standing on the highway, you could say “Gee, the cars are coming at a frequency of 5 cars per minute”. Your friend might say, “Yeah, I noticed they are very close together”. The frequency is the rate they go by and the wavelength is the distance between the cars.

All the frequencies (or wavelengths) of light are called the Electromagnetic Spectrum. That’s because light is an electromagnetic disturbance (whereas sound is a mechanical disturbance). In fact, you can impress your friends by calling light “electromagnetic radiation”. Here’s a typical picture of the different names that light gets called when it is at different frequencies.

So our example of green light above which was 540 THz has a wavelength of 555nm. That’s 555 Nano Meters which is very small. So the distance between each disturbance as the light travels is 555 nm which is microscopic.

In fact human eyes tend to have four different kids of sensors that each have their own range of sensitivity to frequency.

500–700 nm (lower frequency but higher wavelength, “cones” in your eyes)
450–630 nm (“cones”)
400–500 nm (higher frequency, “cones”)
xxx-xxx nm (note this is a wider range, its the “rods” in your eyes)

Color is just the experience you have when these four sensors are stimulated in different combinations.

The first three sensors ranges listed give is the most perception of color.

Some combination of frequencies of light can give the perception of red. Other combinations can give a perception of green and blue.

This “red”, “green” and “blue” light can be added to produce other color experiences.

So if take the “red” and add the “green” to it and shine it in our eyes, you will percieve “yellow”.

This is called “Additive Mixing of Colors” and this is how your computer monitor works and that’s why it’s called an RGB monitor.

Eyeball the diagram below. On the left side is a diagram showing the colors for additive mixing.

These “primary colors”, red, green and blue produce, yellow, cyan and magenta as “secondary colors”. They call them secondary because you’re just mixing two primary colors.

Notice at the middle of the diagram, there is white. That’s what you get when you mix all three of these primaries.

Skeptical? Go dip your finger under the tap and put a drop of water on your computer screen on the color yellow. The droplet will magnify the screen and you will see that there are little red and green lights glowing on the screen to produce yellow. Put the droplet on the white part of your screen and you will see all three primaries, red, green and blue.

This is adding different colors of light.

Mixing paint on the other hand is a different game. When we look at pigment we see color because of what it absorbs. For instance a red pigment is absorbing light that isn’t red and is reflecting the red light. So when you mix two pigments together, it’s absorbing even more light. That changes things around.

To get effective color mixing using this “subtractive” method, we take the three secondaries from the additive method  (cyan, magenta and yellow) and and use them as primaries. See the right side of the diagram above. You’ll observe with this method, the secondary colors are the primaries from the additive method! What a crazy world we live in!

Further, when all three primaries cyan, magenta and yellow are mixed with this method it produces black. In practice it doesn’t work well to get black unless the pigments are perfect. This is why color printers have a black cartridge in them. Instead of putting out three different colors (using a lot of ink to produce a poor quality black), they just add a black cartridge.

Now you know why your printer has 4 colored ink cartridges in it (some have integrated cartridges with all 4 in one).

These are often labeled as CMYK. It stands for Cyan, Magenta, Yellow and Key which refers to the black. How about them apples?

What is color? (part II)

So as you can see it’s not that complicated. But when you get to applications, light sources and pigments are not that predictable so can be a difficult problem.

Painters have had to deal with this since the beginning. Some of this theory explains why certain memes in painting exist.

One method that has been used in the 16th century is grisaille. With this technique the artist is using a vary narrow pallet. It sort of the 16th century version of black and white. Because of the narrow pallet, this technique avoids the issues of pigments and light (to some extent) and is a great technique for creating 3d experiences. Especially with sculpture since it is already usually mono color.

Chiaroscuro (or Tenebrism) is another interesting technique. With Chiaroscuro, the artist uses a great amount of contrast. The background is very dark and the foreground is very bright. Be sticking to these two extremes, the subject of the painting becomes very clear. It also decreases the demand on the palette since everything is very dark or very light. Less concern for shadows and other challenges.

Sfumato is a technique that blurs the areas of bright and dark so that it appears foggy (in a sense). This is another method of removing certain details to make things more realistic.

There is another technique I find interesting where the artist doesn’t use shading. They just use a different color. I can’t remember what it’s called so I’ll look it up and revise this article. 🙂



Web: The resolution of monitors has been an issue and there is a palette of “safe colors”. Also, here’s a cool way of coming up with colors for a site.

It’s easy to use and it shows color wheel spacing and such.

I think it could serve as a good starting point for any project.