Simplifying Complexity, One Answer at a Time!
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It's just the concept of additive color mixing vs subtractive color mixing.
Adding pigments together will ultimately create black. While adding more light together will ultimately make white.
With pigments you're taking away from the color space. You paint red to subdue all other colors except for red.
But you use red light to make sure red is better seen.
It's kinda cool (to me at least lol) how literal the terms "additive" and "subtractive" for color mixing are. With additive mixing (such as on a computer screen), you start with black and add the primary colors (RGB) in different combinations. If you add all of them you get white.
Subtractive mixing (like pigments) starts from white and "subtracts" those same RGB colors. You can think of cyan, magenta, and yellow as "minus red", "minus green", and "minus blue" respectively, since that's which wavelengths thise pigments absorb. So mixing cyan and magenta for instance gives you "white (RGB) minus red minus green", which leaves only blue.
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.