Im always confused by RGB. I learned that if you want orange, you mix red and yellow. If you want green, you mix blue and yellow, if you want purple, you mix red and blue.
How is it that computers need green and not yellow?
Technology Connections has a couple interesting videos on the subject. Here’s one focused on the color brown with an explanation of additive vs. subtractive color (mixing light vs. pigments) starting around this timestamp. There’s also this video with some cool demonstrations using RGB LEDs and some common household objects.
Computer screens emit light, so when your computer shows a green LED next to a red LED, both green and red light wavelengths are sent to your eyes, and your brain interprets this as yellow. This is because your eyes only have red, green, and blue receptors in them, so sending green light mixed with red light is indistinguishable from pure yellow light.
Pigment, instead, works by absorbing light. The trick is that red, yellow, and blue are not the primary colors of light–it’s instead Cyan, Magenta, and Yellow (which look similar to Red, Yellow, and Blue). Yellow pigment absorbs blue light, magenta pigment absorbs green light, and cyan pigment absorbs red light. Therefore, if you mix yellow and cyan pigments together, the resulting mixture absorbs the blue AND red light, so green is the only wavelength left that gets reflected back and picked up by your eyes.
I found a video on it that explained this well with a neat diagram: https://youtu.be/YtH9eXWuf3Y?t=44
Also how did the “o” from the word “color” in my title make its way to the end of the sentence? 😂
Basically there are two color models, additive and substractive. RGB is additive - turning on red it triggers the red receptors in the eye. If you turn on all three it triggers all your color receptors and you’ll see white. That is all the visible spectrum, if you look at the Sun (which you shouldn’t) you perceive it as white even if the maximum of the emission is at green.
When mixing paint (subtractive model, like CMYK on printers) if you mix all colors, they absorb different part of the light and don’t reflect anything visible for you, and you’ll see black(ish)
Computers make yellow with red + green…
Btw the three colour channels, red, green, blue each have 8 bits, 2^8 = 256. And for all three channels there are 256 x 256 x 256 = 16,777,216 permutations of possible colours.
If you have a Mac you can use Colour Picker (in Applications/Utilities) to hover over your screen and see the channel mixes of colours under the cursor.
