Quote - but we don't render by wavelength. We render using only three primaries and a red primary, for example, it is not only a red light, it has the peak in the red spectrum, but has also orange, yellow, green and even blue colors, even with smaller intensities. If we change the R intensity we are changing also the blue intensity. We are not able to change the red color without changing the other colors that makes part of the primary. The same thing happens with Green and Blue primaries.

Which is why renderers like Maxwell render in spectra instead of RGB (part of the reason for their ridiculous levels of photorealism)