Sky blue
- HEX
- #87CEEB
- RGB
- 135 206 235
- HSL
- 197° 71% 73%
- CMYK
- 43 12 0 8
Sky blue or Aqua?
Softer than aqua, without its green tint.
The color of a clear daytime sky. The historian Michel Pastoureau argues that Europe's elites shunned light blue as faded peasant woad until it became a court fashion in the early 1700s.
Science
Sunlight bounces off the molecules of the air, and short blue waves scatter far more than long red ones, so blue reaches you from every direction. Lord Rayleigh worked out the math in 1871. At sunset the light crosses so much air that the blue is scattered away before it arrives, leaving orange and red. See spectrum.
History
In 1789 the Swiss scientist Horace-Bénédict de Saussure built a cyanometer: a ring of 53 numbered blues, from nearly white to nearly black, for measuring the sky. He took readings in Geneva, at Chamonix and on Mont Blanc, and concluded that the sky's blue depends on what is floating in the air.
Kin
- Cerulean: From caeruleus, the Latin word for the blue of sky and sea
- Orange: The same scattering paints a blue noon and an orange sunset
- Kelly green: Ireland's Order of St Patrick (1783) dressed its knights in sky blue
- Cornflower: France's 1915 sky-blue uniforms gave the cornflower its meaning
Sources
- Strutt (Lord Rayleigh), 'On the light from the sky', Philosophical Magazine (1871)
- Wikipedia, 'Cyanometer'; Colossal, 'The cyanometer is a 225-year-old tool' (2014)
Hex values are screen approximations. Every page lists its sources.