I didnt mean too
I just think the article is misleading, it is right, its not a normal colour its an extra spectral colour, but it is still a colour. Easiest way to explain it is; if white light hits a magenta object, the red and blue wavelengths are reflected, but the green wavelengths are absorbed, so you only receive the blue and red wavelengths, your brain works out the colour as a result. Its easy to do a similar experiment in photoshop, go onto your channels on a blank white RGB document and throw a black fill on the green channel, you'll get a magenta image, this is due to the absence of green from the spectrum, the entire CMYK colour system is based on this kind of colour mixing, subtractive colour, removing one wavelength leaves you with all the others. With subtractive colour, you do not see individual wavelengths in the spectrum, what you see is the result of the entire spectrum with wavelengths missing, the brain decides what these colours are.