system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come when mixing paints, Red + Yellow + Blue = Brown, not Black?

As paint is subtractive (it absorbs all color except the one we see, aka Blue paint absorbs all but Blue), I'd expect that mixing the 3 primary colors would result in ALL color being absorbed, resulting in Black.
gpt
Paints don’t absorb *all* except the colour we see, it’s a pretty wide spectrum. They just absorb most. As a result, even if you mix colours, you still reflect some of everything so you get brownish. 

To get black you need to switch chemistries entirely to things that don’t reflect at all.