Blue, Rebecca Solnit wrote in one of humanity’s most beautiful reflections on our planet’s primary hue, is “the color of solitude and of desire, the color of there seen from here… the color of longing for the distances you never arrive in, for the blue world,” a world of many blues — a pioneering 19th-century nomenclature of colors listed eleven kinds of blue, in hues as varied as the color of the flax-flower and the throat of the blue titmouse and the stamina of a particular species of anemone. Darwin took this guide with him on The Beagle to better describe what he saw. We name to see better and apprehend only what we know how to call and think about.
But despite Earth’s distinction as the Solar System’s “Pale Blue Dot,” this planetary blueness is only a perceptual phenomenon arising from how our particular atmosphere, with its specific chemistry, absorbs and reflects light. Everything we behold — a ball, a bird, a planet — is the color we perceive it to be because of its insentient stubbornness toward the spectrum because these are the wavelengths of light it refuses to absorb and instead reflects back.
In the living world beneath our red-ravenous atmosphere, blue is the rarest color: No naturally occurring actual blue pigment in nature. In consequence, only a slender portion of plants bloom in blue. An even more negligible number of animals are bedecked with it, all having to perform various tricks with chemistry and the physics of light, some having evolved astonishing triumphs of structural geometry to render themselves blue: Each feather of the bluejay is tessellated with tiny light-reflecting beads arranged to cancel out every wavelength of light except the blue; the wings of the blue morpho butterflies — which Nabokov, in his spree of making significant contributions to lepidoptery while revolutionizing literature, rightly described as “shimmering light-blue mirrors” — are covered with tiny scales ridged at the precise angle to bend light in such a way that only the blue portion of the spectrum has reflected the eye of the beholder. Only a handful of known animals, all species of butterfly, produce pigments as close to blue as nature can get — green-tinted aquamarines the color of Uranus.