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Why is the sky blue, and sunsets red? (for a curious adult who has never studied physics). Cover, in this order: What is white light made of?; What does air do to a beam of light?; Why does blue light scatter more than red?; So why isn't the sky violet?; Why are sunsets red?; Why are clouds white? — page 4: Why Not Violet
Violet scatters most, but sunlight holds less violet than blue, and our eyes respond more to blue. So the sky looks blue.
First, sunlight isn't an even mix. The sun emits less violet than blue. Scatter it hard, but you're still starting with a smaller supply.
Second, our eyes. The cone cells that sense color respond far better to blue than to violet, so violet light barely registers.
Violet scatters the most, but there is far less of it and our eyes see it poorly, so blue wins. That balance is why the sky looks blue.
So the blue sky is partly a fact about air and sunlight, and partly a fact about us: the color we call the sky's is the one our eyes handle best.