You see colour using three different kinds of cones in our eyes, and these cones can be either red, blue, or green. So where does yellow come in? Green consists of yellow and blue – but how would you only see yellow and not the blue that would make it green?
In: Biology
There are two sets of primary colors: Additive and subtractive. Additive primary colors are Red, Green and Blue. Most people learn about Subtractive Primary Colors as Red, Yellow and Blue, but more accurately its Cyan, Magenta and Yellow. We’ll come back to this in a bit.
Additive Primary Colors apply when you are combining different colors of light. Pretend you have three spotlights, all aimed at the same spot. One of them is red, another green, and the third one is blue. If you turn on the red light, the spot lights up red. If you add in green light, the spot lights up yellow. And if you add in the blue light, the spot is now white. If you take away the red light, leaving the green and blue, the spot is now a bright turquoise color, called cyan. This is the way you can create pretty much any visible color using three separate lights. Televisions and other video screens exploit this effect by having three different colored lights for every pixel – they’re very small and very close together, but if you look at your screen under a microscope, you’ll see them. And by turning each light on at different brightnesses, you can create millions of individual colors.
Subtractive primary colors are used when combining different colors of pigment – that’s a fancy word for paint. If you combine red and blue paint, you’ll get the color purple. Yellow and blue, you get green. Red and yellow – orange. However, in professional printmaking, the primary subtractive colors they use are actually Cyan, Magenta, Yellow, and Black. This allows for the creation of the same range of colors as you can with light, but instead you’re mixing paint.
There’s some argument to the idea that we never actually “see” yellow, because we only have cones for red and green – instead our brains just combine the two activated sets of cones and fills in the details. I can’t speak much to this because I don’t understand the physiology of the eye nor the cognitive processes that augment it.
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