Magenta has no place on the rainbow; your brain invents it
No single wavelength of light looks magenta. The colour appears when your eyes pick up strong blue and some red with little green in between, and the brain fills the gap. Its name comes from a bloody 1859 battle in Lombardy, borrowed by dye makers riding the first boom in synthetic colour.
Physiologically, magenta is extra-spectral. It arises when short-wave blue cones fire, long-wave cones respond weakly to the same deep blue, and middle-wave cones stay mostly quiet. Depending on the balance, the brain reads the mix as magenta or purple. The Munsell system simply calls it red-purple. Because it sits opposite green, a particular magenta light added to the matching green light yields white.
The dye came out of a chemical gold rush. William Perkin's mauveine of 1856, the first synthetic aniline dye, sold so well that chemists across Europe hunted for more. Near Lyon, Francois-Emmanuel Verguin combined aniline with carbon tetrachloride in late 1858 or early 1859 and called the reddish-purple result fuchsine, after the fuchsia flower. In London, Edward Chambers Nicholson and George Maule made a near twin they sold as roseine, then in 1860 renamed it after the French and Sardinian win over Austria at Magenta, fought on 4 June 1859.
Screens and printers disagree about it. On a monitor, magenta is a secondary colour made from equal red and blue light, identical to the web colour fuchsia. In CMYK printing, a system that took shape in the 1890s as newspapers began running colour comics, it is a primary ink alongside cyan and yellow. Printer's magenta is redder and far duller than the screen version, and no ink can match the glow of the electronic shade. Modern paints often use quinacridone pigments, a family developed from 1935.
The hue turns up in unexpected places. Tropical flowers favour it because it contrasts most sharply with green leaves, making blooms easier for pollinators to spot. The coolest T-class brown dwarfs look magenta because sodium and potassium soak up green light. Cockpit autopilot displays draw the planned route in it, London's Metropolitan line wears it, and Deutsche Telekom has tried to stop even an insurance firm, Lemonade, from using a similar shade.
Source: Magenta
