https://en.wikipedia.org/wiki/Blue " It lies between violet and green on the spectrum of visible light. Dark blue became a common colour for military uniforms and later, in the late 20th century, for business suits. Because blue has commonly been associated with harmony, it was chosen as the colour of the flags of the United Nations and the European Union."
"Surveys in the US and Europe show that blue is the colour most commonly associated with harmony, faithfulness, confidence, distance, infinity, the imagination, cold, and sometimes with sadness. In US and European public opinion polls it is the most popular colour, chosen by almost half of both men and women as their favourite colour. The same surveys also showed that blue was the colour most associated with the masculine, just ahead of black, and was also the colour most associated with intelligence, knowledge, calm and concentration."
"Prussian blue, the colour of the uniforms of the army of Prussia, was invented in about 1706" "Of the colours in the visible spectrum of light, blue has a very short wavelength, while red has the longest wavelength. When sunlight passes through the atmosphere, the blue wavelengths are scattered more widely by the oxygen and nitrogen molecules, and more blue comes to our eyes. This effect is called Rayleigh scattering, after Lord Rayleigh, the British physicist who discovered it. It was confirmed by Albert Einstein in 1911." "Under the sea, red and other light with longer wavelengths is absorbed, so white objects appear blue. The deeper the observer goes, the darker the blue becomes. In the open sea, only about one per cent of light penetrates to a depth of 200 metres. "
"Blue eyes are most common in Ireland, the Baltic Sea area and Northern Europe, and are also found in Eastern, Central, and Southern Europe. Blue eyes are also found in parts of Western Asia, most notably in Afghanistan, Syria, Iraq, and Iran. In Estonia, 99% of people have blue eyes. In Denmark 30 years ago, only 8% of the population had brown eyes, though through immigration, today that number is about 11%. In Germany, about 75% have blue eyes."
"In Egypt blue was associated with the sky and with divinity. The Egyptian god Amun could make his skin blue so that he could fly, invisible, across the sky. Blue could also protect against evil; many people around the Mediterranean still wear a blue amulet, representing the eye of God, to protect them from misfortune."
"The Ishtar Gate of ancient Babylon (604–562 BC) was decorated with deep blue glazed bricks used as a background for pictures of lions, dragons and aurochs." "The Greeks imported indigo dye from India, calling it indikon. They used Egyptian blue in the wall paintings of Knossos, in Crete"
"The Romans also imported indigo dye, but blue was the colour of working class clothing; the nobles and rich wore white, black, red or violet. Blue was considered the colour of mourning, and the colour of barbarians. Julius Caesar reported that the Celts and Germans dyed their faces blue to frighten their enemies, and tinted their hair blue when they grew old." "Another important factor in the increased prestige of the colour blue in the 12th century was the veneration of the Virgin Mary"
