In elementary/middle school art class, I was taught that the primary colors were yellow, blue, and red. I was a little curious as to why RGB was chosen as a basis instead of yellow, blue, and red, but apparently it's partially due to the physical properties of paint which favor a subtractive color system (whereas our displays/monitor tradition favors an additive system) and also partially due to tradition. (Source: http://wtamu.edu/~cbaird/sq/2015/01/22/why-are-red-yellow-and-blue-the-primary-colors-in-painting-but-computer-screens-use-red-green-and-blue/)
This reminds me the reason why the red light indecates "stop"
@sunsarah, thanks for linking that article! Apart from what you mentioned it also taught me something new - even know the cone cells in our eyes detect RBG, we can see millions of colors because of the cone cells can also detect a bit of other colors, and we see the "combination" of all those colors! Thus, the color systems that work best are those that have its basis in RGB!