Why Purple is So Hard for Animals to Make

What the film says

1. Animals produce color with pigments and with microscopic structures (structural color); peacock feather iridescence is structural.

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2. The purple-breasted cotinga's purple comes from a keratin–air nanostructure that scatters blue-green light combined with the carotenoid pigment cotingin, without melanin.

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3. Male purple emperors have a purple-blue iridescent sheen that females lack.

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4. Only the male purple emperor's upper wings carry the specialized scales, whose reflection peaks at around 380 nm within an angle of about 18°.

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5. For more than a century, the mandrill's blue skin color was attributed to Tyndall scattering.

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6. Purple, unlike violet, is not a spectral color: it has no single wavelength and is perceived as a mix of red and blue.

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