my reasoning: the actual colors we can see -> the wavelengths that we can extrapolate to -> basically extrapolated wavelengths plus an 'unpure-ness' factor -> not even real wavelengths (ok well king blue and maybe lavender if I'm being generous could be)
yea, if there is a single wavelength and its yellow we could see it. However, if you had a full spectrum of light and took away all of the yellow but added some red and green you wouldn't be able to tell that there's no yellow, because we can't see yellow, only imply it from the red-ness and green-ness
i'm pretty sure you couldn't pull off the same trick with red, green, or blue but I guess I don't really know