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The Color Theory — Why do Computers use RGB instead of RYB?

Red, Yellow, and Blue — Primary colors. That’s what we have been told in our kindergarten, isn’t it? But there is more to it. Do you know?

Source Unsplash

If you’re a developer, you might be aware that the computers use the RGB system. Now the question is — if RYB is the primary color set then why do computers use RGB instead?

Going deep into the line, we first need to understand the color theory. There are two different theories -

  1. Additive
  2. Subtractive

Before elaborating that, let me ask you- what exactly is Light? or more specifically the visible light, like the one you see while reading this article. Without diving into electromagnetic radiations, wavelengths, and such other stuff of physics — light is just the color ( Colour ) that is reflected in our eyes.

Here is the deal — as players depend on the game, plants depend on the environment — We too have a different thesis for Primary Colors, depending on the situation. Different cases of Light & Paints ( or inks ).

“We see because light enters our eyes,” Stephen Westland, Professor of Colour Science at the University of Leeds says. “Light enters our eyes in two ways: (1) directly from a light source; and (2) reflected from an object. This leads to two types of color mixing, additive and subtractive.


When we mix paints or inks, subtractive mixing results. Paints or inks are non-emissive objects here. They reflect when light falls on them. Molecules of paint absorb some of the wavelengths of light and reflect rest. That’s how we see such objects.

The primary colors of the subtractive mix are — Red Green Yellow. No. They are CMYK — Cyan, Magenta, Yellow, and K which stands for black ( To distinguish it from B for Blue. Just a convention )

When the CMY ( not K ) gets mixed, it produces brownish color. Bit muddy. To get the more blackish color, the additional K for black is used. CMYK — the model used by printers & publishing houses.

Source Intranet


The additive is the case of the projection of one or more colored lights ( wavelengths ). These are the colors when mixed produce more light. The RGB, Red-Green-Blue when mixed produces lighter colors, resulting in white light at the end. & that’s how our computer, TV, and other light-emitting screen works.

When light is emitted from a screen, it uses an additive color system. If you want to see a color ranging near to purple, the system should emit red and blue lights together.

As you know, most electronic screens are dark, the RGB model is used to emit light. Combining these colors to produce lighter colors offers a good contrast to the dark screens.

Things should have made sense to you by now. But to summarize,

The RGB standard is used when the light is GENERATED; the CMYK standard is for light REFLECTED.

Electronic devices generate light; a printed page reflects light.

You got this. But —

What if I used black paper for printing?

We can’t wait for the light to get printed on black paper. Light can’t be painted on a surface ( sarcastically ). Thus we still need to use ink.

How about using white ink on black paper?

Source — Printer inks are hard. Even if you choose to use white, chances are that paper will soak the ink. But the laser printer can do this.

but, but, what about RYB?

Well, that’s a kindergarten story. The colors of colors are not so easy to color down. But RYB will still be considered as primary colors — taking the perspective of ART.

Now you know the grown-up story. Here are the resources to know more about COLOR or COLOUR.

  1. Color Models by Pavilion
  2. Additive Vs Subtractive by differenceBetween
  3. Black paper printing by crafts StackExchange
  4. Color Theory by science HowStuffWorks
  5. Color Printing by Britannic

With that, I bid adieu.



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