Eli5: What is color theory and how does it work?

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Eli5: What is color theory and how does it work?

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Color theory is all about how different colors interact with each other and the viewers eye. Some of color theory is about colors relationships to each other, what looks good together, how to mix up a specific color, etc. Another part of it is knowing how to adjust the hue of a color to make it look more in shadow, further away from the viewer, etc. Color theory is pretty broad

I think the first point to make is that colours don’t exist. There’s no such thing as red light, for example, there’s just light that our eyes perceive as red. So colour theory isn’t really about how the world behaves — it’s all about how our visual system works, and how we see the world.

I expect you’ve seen the colour wheel:

https://en.wikipedia.org/wiki/Color_wheel

These arrange all possible colours in a circle, with red and green opposite each other, and then at 90 degrees, yellow and blue opposite each other. They usually have a neutral colour at the centre (black or white or grey) and use the spokes to show saturation (how vivid a colour is).

These were originally devised way way back by painters as colour matching guides, but interestingly it turns out they have a biological basis.

The optic nerve carries visual information from the eye to the brain, and we know (from some rather gruesome dissections) that colour is represented by three separate nerves — one does lightness, one does redness-greenness, and one does yellowness-blueness.

So the colour wheel that painters made is actually a map of the signals on the optic nerve. Painters were really describing their own visual system! Signals on the lightness nerve go into and out of the sheet of paper, and the yellow-blue and red-green signals do left-right and up-down.

This is the biological basis for contrasting and complementary colour. Red and green side by side can be almost painful to look at because a single nerve has to constantly flip states. Red and blue are carried by separate nerves, so they are much less disturbing next to each other.

There’s loads more, of course. The human visual system is very complex and often bizarre.