system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do screens use red/blue/green pixels but printers use red/blue/yellow ink?

i know that my computer screen makes the colour white by combining red, green and blue light.  but in art (and my computer printer), the 3 primary colours are red, blue and yellow?

these two setups seem so similar, but with one obvious difference. what gives?

i do remember being told that this difference exists in high school physics, but not "why". if you can ELI5, i'll be happy and a fair bit impressed as well!
gpt
Inks subtract color, screens add. Basic ink colors are cyan, yellow and magenta. So cyan is white minus red, but on a screen it's constructed as blue plus green. It works like this because white light goes through ink, so the color comes from what is subtracted. On a CRT or LED screen, a pixel is a tiny lamp of red, green or blue color, so the color comes from what is added to black (screen off). Also, pixels are monochromatic on LCD screens even though they absorb light.