The BROWN in the rainbow
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If you have a look at a rainbow, you won't see any brown. It isn’t part of the ROYGBIV (red, orange, yellow, green, blue, indigo, violet) list we learned as kids.
The colors you do see in the rainbow appear when light from the sun is bends as it contacts moisture, splitting the light into its component wavelengths.
All colors in the rainbow (called spectral colors) are associated with a particular wavelength of light. Red light has a longer wavelength and blue light has a shorter wavelength.
The colors we see out in the world that don't appear in the rainbow (nonspectral colors) are made by combining multiple wavelengths together.
Magenta is strictly nonspectral: we can perceive it when short wavelength and long wavelength light appear simultaneously
Given the absence of brown in the rainbow, you might expect that it is nonspectral, like magenta is.
Maybe the only way to make brown is to combine multiple wavelengths together.
However, brown is—in a way—right there in a rainbow. It can is associated with a single wavelength of light.
So why can't you see the brown in the rainbow? The answer depends on how our eyes and minds create our experience of color.
Color theorists typically describe colors based on their:
- hue: this is what people typically mean when they say "color". Different hues are shown as you move around the color circle shown
- saturation: this refers to purity or how far the color is from white. More saturated colors are shown on the outer edge of the ring, less saturated colors appear near the center.
- brightness: this represents the total amount of light present. Darker colors are lower on brightness.
Hue, saturation, and brightness all vary independently.
Red and orange differ in hue.
Red and pink differ in saturation: pink is a whiteish red
Red and maroon differ in brightness: maroon is a dark red
So how do we go from one of the fully saturated, bright colors you see around the edge of the color circle to brown?
We start with orange, and turn down the brightness.
Brown is just dark orange.
We transition from brown to orange by changing the amount of light present.
However, whether something looks brown or orange may also depend on what the color is being compared to.
The square shown to the right may look rather brown when set against a white background.
But when the background is black, it looks more like orange.
The square is the same in both cases, but your perception of it changes based on what it is being compared to.
Here's another example. In the checkerboard below, the two circles are exactly the same color (hue, saturation, and brightness).
However, we tend to interpret the one near the bottom as brighter (more orange) than the one near the top.
The one nearer the bottom appears to be in shadow, so we are correcting for that perceived darkness and seeing it as brighter (oranger) than it is.
Is it surprising that brown and orange are so closely related? This may be because we have different basic color words for brown and orange.
It’s not surprising that starting with red and turning down the brightness leads to . . . dark red. Even if we call it maroon instead, it isn't surprising that making red somewhat darker leads to maroon, because we generally think of maroon as a type of red.
Not so with brown; most people would not describe brown as a type of orange.
Brown and orange feel psychologically different in a way that most shades that share hue and saturation don't.
This may be partially driven by our language.
The English word for brown comes from Old English and has been used as a color term since 1000CE.
In contrast, the word "orange" didn't exist in Old English. The closest thing was "geoluhread” (yellow-red).
In 1390, Chaucer described a fox as having a color “color was betwixe yelow and reed" because there didn't yet exist in English a word specifically for orange.
But by the mid 1600s, the word was commonly used in English. What happened between 1390 and 1600?
Portuguese traders brought sweet oranges from India to Europe, and English speakers had our first contact with the fruit!
So the color term orange takes its name from the fruit.
The fact that English didn’t have a name for the color orange until the 16th century means that things that are actually orange that were named before then are often called red instead!
Red hair, robin redbreasts, and red squirrels are all orange, but we've been talking about them since before a word for orange existed in English.
Photo by Jonny Gios on Unsplash
Photo by Jonny Gios on Unsplash
Photo by Joshua J. Cotten on Unsplash
Photo by Joshua J. Cotten on Unsplash
Because we were talking about brown things long before the word for orange entered the language, the distinction may have become more pronounced than it actually is.
So the wavelengths associated with brown are indeed hidden right there in the rainbow, but the brightness and our mental representations of color prevent us from seeing it!
Created by Julia Strand, PhD
Carleton College, Northfield, MN, USA
More explainers: juliastrand.com/explainers
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