People who have a bit of a clue about how human colour vision works know that the "purple doesn't exist" factoid is bullshit. No, that's not facetious; that's the proper technical term: "Purple doesn't exist" isn't <i>wrong</i> — it's <i>not even wrong</i>. It's a writing prompt for pseudo-scientific blog spam; it's bullshit.<p>Ideally, you'll have had a high-school education featuring a biology teacher explaining the stuff with the rods and the cones and an art teacher explaining colour theory, so you can just put two and two together. But if you haven't had that privilege, there's good news: Instead of enduring a harried rant by some random HN commenter, you can just lean back and watch a short lecture from an excellent science educator: <i>Why you can't take a good picture of a rainbow</i> by Steve Mould.<p><a href="https://www.youtube.com/watch?v=HauiF_AQUIY" rel="nofollow">https://www.youtube.com/watch?v=HauiF_AQUIY</a>