3D glasses

I went to the cinema with herself last night to see Sherk the Third (not great movie) and they had the "first ever" 3D add. It was for Red Bull flying race or some such thing. Anyway I realise how it works. Basically colours focus at different depths in the eye. So to focus them the lens of you eye has to adjust itself to focus them. So when you put the glasses on you are only seeing red in one eye and green in the other. As these wavelengths are going to be focused at different depths.each eye is going to be focused differently. Thus when the image on the screen is shown with different colours they are going to be focused at differently in each eye giving the illusion of perception. Genius I think. (I think this is the way it works if anyone cares to differ with me please tell me.