How camera calculates amount of color per pixel
The camera measures the amount of light in each 'bin', red blue or green, and that is the amount of light that your monitor should emit from the red, green and blue pixels in its display in order to be perceived by your eye as that original color. 

This only works because the human eye has receptors for red, green and blue light, and that's how it sees color. The spectrum is certainly not necessarily the same for the light emitted by the monitor as what was originally measured. 

For example, sunlight has a spectrum that looks like this: 



But white light from an LCD display has a spectrum that looks like this: 



It's a little more complicated than that because the filter colors in the display and camera don't match the eye response exactly.