# Mixing Different Solutions with Different Wavelengths to Get Different Colors?

I recently was told that the reason you can mix colors (blue and yellow make green because wavelengths 605nm + 450nm = green) was based on wavelength (which seems very obvious when you think about it but please humor me).

This is kind of cool but I don't get it - is this based on the wavelength range that's transmitted? If 605nm + 450nm = green then how would you find that exact wavelength of green? Would it be the average of the two, or is there some constant that I am missing?

1. Subtractive mixing is observed when you mix two coloured solutions ot put two colored films on top of each other and shine white light through it. Here, $\mathrm{\color{yellow}{yellow}}$ and $\mathrm{\color{blue}{blue}}$ yield $\mathrm{\color{green}{green}}$.
2. Additive mixing is observed when you overlay two coloured light sources. In the RGB model, $\mathrm{\color{red}{red}}$ and $\mathrm{\color{green}{green}}$ yield $\mathrm{\color{yellow}{yellow}}$, the combination of $\mathrm{\color{red}{red}}$, $\mathrm{\color{green}{green}}$ and $\mathrm{\color{blue}{blue}}$ yields white.