Are there really seven colors in the rainbow?
Are there really seven colors in the rainbow?
We demystify the colors in the rainbow, explain how they got there and tell you exactly how many colors there are.
In school we’ve learned there are seven colors in the rainbow. They go under the acronym ROY G BIV which stand for:
- Red
- Orange
- Yellow
- Green
- Blue
- Indigo
- Violet
Now, light is nothing more than a flow of small particles called photons. They are a type of radiation - if you want to get a tad technical you can think of radiation as molecules in vibration. Or waves, such as heat, radio and microwaves, which all sit on a spectrum.
Now, out of all the waves on this spectrum, our eyes can only see a small portion of them. That’s called the “Visible spectrum”.
“But why is that?” I’m hearing. Thanks for the question. I’ll answer it pronto.
Our eyes’ retinas have photoreceptor cells which are called “cones”, because of their shape. As suggested by the biological term, these cells can receive photons and, through a complex metabolic process, convert them into signals for the brain. These signals are exactly what we perceive as colors.
Our eyes have three types of photoreceptors, each capable of decoding a certain photon or light frequency. Put simply, one type of cone sees Red, another one sees Green, and the third one sees Blue.
Hang on a second, so if we only have three types of photoreceptors each capable of “detecting” one color, where are the other four colors from the rainbow (and the spectrum) coming from? And where do the other colors like Brown and Black come from?
Let’s answer the first question.
Our cones don’t just perceive Red, Green and Blue in isolation. They can also see how the Red, Green and Blue photons blend with each other in different proportions. This explain where all colors of the rainbow come from:
- Red - not combined with other colors
- Orange - a combination of Red and Green
- Yellow - a different combination of Red and Green
- Green - not combined with other colors
- Blue - not combined with other colors
- Indigo - a combination of Blue and Red
- Violet - a different combination of Blue and Red.
- As you can see, we’ve just illustrated how additional colors can be created by “mixing” Red, Green and Blue together.
This also explains why birds, which have four types of photoreceptors, can technically see nine colors. And one of these colors sits in the UV spectrum!
We’re finding some answers. But you might want to know more, especially if you’ve heard of the additive vs subtractive model; different sets of primary colors for print and for screen; RGB and CMYK; etc. It can be very confusing, but we can explain it all, don’t you worry.
Additive VS subtractive color models
The reason why we have two color models is that colors behave differently depending on their chemical composition. Another way to say this is that different models apply to different types of objects.
Objects that emit light, such as TV, computer screens or projectors work in line with the additive model.
As the name of this model suggests, when you add the primary colors (Red, Green, and Blue) to each other, secondary colors are created.
This image shows what happens when you project three beams of light on a white wall.
Notice how Yellow, Purple and light Blue are created at the intersection of the three beams of light. And when the three primary colors perfectly overlap, they produce transparent white light. This process is very similar to the one you see when light is refracted through a prism, or in a rainbow.
Now this is the case of “colored light”, but what happens when we deal with material colors, such the ones used by painters or by our printers, from the most common to the large industrial ones?
We go in the realm of subtractive colors, so called because they reflect less light when they are mixed (in other words, certain wavelengths are absorbed, or subtracted from what we see). Here is an example that clarifies what we mean.
Painters, or kids in school, take the subtractive primary colors (Blue, also called Cyan; Red, also called Magenta; and Yellow) and mix them together to create the other colors.
As the colors are progressively mixed, the light gets absorbed, creating colors that are gradually darker and duller. See why it is called “subtractive”? Now you also understand why mixing all colors in equal proportions results in the color Black.
Notice that I’ve used the words “primary colors” for both models. Is this a contradiction? Not at all. The two different systems have two different sets of primary colors. In both cases these are the colors that cannot be made by “mixing” the other colors (whether they are in the form of light or paint pigments).
Subtractive Color Model:
Used for objects reflecting light.
Paint, print and objects.
Creates colors by mixing pigments or ink and absorbing light.
The more pigment or ink is added, the darker and closer to Black the colors become.
Primary colors: Cyan, Magenta, Yellow (what in primary school we learn as Blue, Red and Yellow).
And if you really want to delve into the subject, check out this pretty cool article on primary colors.
Feels like we know a bit more about the science of colors, doesn’t it? Now we’re ready to go deeper and find out if there really are seven colors in the rainbow.
How many colors are in a rainbow?
First, take a moment to admire one of Nature’s masterpieces. Isn’t it incredible?
Now, looking at the rainbow closely, you might realize there’s actually more than seven colors.
That’s because each color blends into the other gradually. This creates many more color combinations - you can call them color graduations, or hues.
So why do we say there are only seven colors in the rainbow?
Who settled for seven colors and picked exactly those, when there are so many nuances? Indigo and violet, I’m looking at you!
Ancient Greece and the number seven
Pythagoras, the greek philosopher from the 6th century BC, believed that numbers were intrinsically connected to both the physical and the metaphysical worlds.
They represented means to investigate and interpret the physical dimension, but were also a way to access the universal truths.
Pythagoras divided creation into planes or spheres, and assigned to each a tone, a harmonic interval, a number, a name, a form and a color.
Isaac Newton
The English physicist and mathematician Isaac Newton (1643–1727) was the first to approach colors from a scientific point of view. In a series of experiments with sunlight and prisms, he showed that clear white light comprised seven visible colors.
But Newton didn't stop there. He tried to demonstrate the connection between colors and the seven musical notes.
You could see how he was influenced by Pythagoras in this belief. In fact, Newton initially talked about only five colors in the spectrum: Red, Yellow, Green, Blue and Violet.
The link between colors and sounds
Throughout the centuries, philosophers, scientists, writers and musicians have searched for the connection between musical notes and colors, as a key to access Nature’s universal principles.
They all tried to prove that white light was made of seven colors:
The Russian composer and pianist Scriabin thought that each note in the octave could be associated with a specific color.
Debussy and Wagner also researched the interrelation between music and color.
The Rosicrucian Order identified exact Hertz frequencies for notes and colors.
The philosopher Charles Fourier in his “Théorie de l'Unité Universelle” associated colors to musical notes and metals.
The answer to how many colors in the rainbow.
Imagine rain droplets as a multitude of micro-prisms that come together to break the rays of light into its constituting parts.
That’s exactly what happens when we look at the rainbow and admire its colors. If we look at that spectrum carefully, we notice that in between the famous “seven colors of the rainbow”, there’s in fact many more.
Influenced by Pythagoras and the classical world, our culture has upheld the number seven as a means to organize knowledge and connect us to Nature’s universal truths.
Goethe and others challenged this concept - and perhaps today science proves them right.
There are indeed more than seven colors in the rainbow, but we keep referring to these seven. Maybe it’s out of habit, or maybe because it’s easier that way.
I might just be influenced by our culture, but seven sounds like a good number, doesn’t it?
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