Purple doesn’t exist

Why doesn’t magenta appear in the rainbow? The answer lies not in physics but in biology. Science presenter Steve Mould demonstrates the strange phenomenon of colour mixing, in which not everything is as it seems. The cone cells within our eyes are responsible for the colours we see, but are only sensitive to Red, Green and Blue light. So how are we able to see so many colours when we can only directly detect three and how do our brains see the colour magenta which doesn’t have a wavelength? Steve explain