Magenta Ain't A Colour, article. Kewl.
What a completely muddled load of nonsense. Of course the eye doesn't detect the wavelength of the light as such - it detects the responses of the three types of colour receptors (red, green and blue cones) and assigns a perceived colour based on those.
Magenta is a colour. It's just not a "pure" colour - one which can be represented by a single wavelength of light.