eli5: why do we use red green blue instead of the primary colours for light

Question

i kinda understand the difference between subtractive and addictive colours but i don’t understand why we use green instead of yellow for lights

In: Other

Answer 1

Red, green and blue ARE the primary colors, we have receptors in our eyes that react to the wavelengths we call RED, GREEN and BLUE, the thing is that those receptors don’t only react to a single wavelength but many in different degrees so when you get a wavelength between green and red it activates both at the same time and your brain interprets it as yellow. In the same manner you can use a green light combined with a red one and since you’ll be activating both green and red receptors your brain will interpret it as yellow, this is called ADDITIVE color because you are adding light.
In graphic design we call CYAN, MAGENTA and YELLOW primaries because for printing we use SUBSTRACTIVE color, you start with white which reflects all the wavelengths and add pigments that absorbe some of them while reflecting only a few, the more pigment you add the more light you remove, in this case when you add yellow to a paper you are adding a pigment that absorbs all light except for the wavelength that corresponds to yellow light.