Here's something weird... Technically, purple is a product of your imagination... Your brain fakes the color purple. Or basically guesses as best it can.
Purple is a "non-spectral color", which means that it exists only in our minds: there is no wavelength of light that corresponds to it. Our brain perceives purple when it sees a mixture of strong red and strong blue light, without any green.
A good explanation, if you have 15 minutes to kill...