optics - Why are color values stored as Red, Green, Blue?

I learned in elementary school that you could get green by mixing blue with yellow.

However with LEDs, TFTs, etc. you always have RGB (red, green, blue) values?

Why is that? From what you learned in elementary yellow would be the 'natural' choice instead of green.

Answer

When you mix colors using Watercolors, then they mix as "Subtractive Colors". However, Light itself mixes as "Additive Colors".

Even though it might seem strange why the inherently same thing works so differently, it makes sense if you think about Watercolors, etc. as absorbing everything but that specific color.