We demystify the colors in the rainbow, explain how they got there and tell you exactly how many colors there are.
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).
The other cool thing to know is that there is a deep correlation between the two models. Consider the below:
Cyan absorbs Red Magenta absorbs Green Yellow absorbs Blue
As you can see CMY (Cyan, Magenta and Yellow) mirror RGB (Red, Green and Blue)!
And what about K, the Black that you usually see next to the primary colors when it comes to our printers? That’s exactly the reason it’s there. With the advancements of the printing techniques, we have learned that a fourth line of color gives the best results in reproducing color shades, tints and nuances.
To recap the two models:
Additive Color Model:
Used for objects emitting light. TV, computer screens, projectors (and our favorite ones, rainbows). Creates colors by adding light. The more light sources are added, the brighter and closer to White the colors become. Primary colors: Red, Green, Blue.
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.
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Sat May 29, 2021 1:20 pm
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