Why do printers have CMYK ink instead of RYB & black ink?
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A monitor emits light so red, green, and blue are added together. So red and green light have the same visual effect on humans as yellow light. This is an additive colors model
Printing use ink that when illuminated by white light reflects back some light and absorbed other. So if you use twixt two ink color only the light both reflect are reflected, this is a subtractive color model
Look at https://www.simplypsychology.org/wp-content/uploads/eye-color-sensitivity.png which shows the color sensitivity of the three types of cones in a human eye.
RGB monitor works by having a color that primarily stimulates one of the cones and you can trick it so that we see color in between. With ink of just three colors, we need to do the same with the three cone types, it just had to do by absorbing parts of red light
https://www.thevisualpro.com/hubfs/Imported_Blog_Media/Which_to_choose_CMYK_vs_RGB_VisualPro.jpg
For ink where light is removed, you reflect light that stimulates two cones in one ink.
Yellow ink in reflecting back both green and red light, that mean is absorbed the light that stimulates the “blue” cone
Cyan lighter reflects blue and green light, so it absorbed red.
Magenta reflects blue and red light, so it absorbed green.
So think of the ink as removing, red, green, and blue light from white. Yellow ink does not reflect back just yellow light, it reflects back light from green to red light includes yellow, it absorbed blue light
The spectra of the ink look like https://www.researchgate.net/publication/359777295/figure/fig4/AS:1143362056929291@1649610165431/Spectral-reflection-analysis-of-cyan-magenta-and-yellow-inks-illuminated-with-31-LED.png so reality us a bit messier than the text above but the general idea is correct
The result is if you what green when you print you use the inks that absorbed red and blue light. Cyan absorbed red and yellow absorbed blue but both reflect green. So cyan ink + yellow ink = green color when illuminated by white light
So the colors that are used are a result of how our eye works and the difference between absorbing light that hit something compared to emitting light
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