In the spectrum, the Yellow Hues fall in the narrow bandwidth from 575 nanometers, to 590 nanometers. The Yellow produced by our spotlights and the Yellow we perceive when we get an equal stimulus of Red and Green is the same, but is not the Yellow of the spectrum.

When Red light with a wavelength of 680 nm is mixed with Green light having a wavelength of 515 nm, the wavelength of the first subharmonic frequency of that mixture's upper sideband will be 586 nm, which neatly falls between 575 nm and 590 nm giving the sensation of Yellow. On the next page I will show you the actual calculations.