50 Fun Facts About Blue

Which optical effect makes the clear daytime sky look blue?

Rayleigh scattering. Air molecules scatter short blue wavelengths far more than long red ones, and at sunset the light crosses so much air that the blue is scattered away and the reds are left.

Which colour of visible light has a shorter wavelength than blue?

Violet. Blue light runs from roughly 450 to 495 nanometres and violet is shorter still, so the 405-nanometre 'blue' laser that reads a Blu-ray disc really sits in the violet range.

What was the first artificial pigment, made more than 4,000 years ago by heating sand with ground minerals?

Egyptian blue. It glows strongly in infrared when lit, so museums can now photograph traces of it on ancient statues that look bare to the naked eye.

Which organisation's flag shows a world map wreathed in olive branches on a light blue field?

The United Nations. Its designers in 1945 chose blue to stand for peace, as the opposite of red, which they called the colour of war.

Ultramarine, the most expensive Renaissance pigment, was ground from which stone?

Lapis lazuli. Ground and washed into ultramarine, it could cost as much as gold, so Renaissance painters often saved it for the robes of the Virgin Mary.

The pigment name 'ultramarine' comes from Latin words meaning what?

Beyond the sea, from the medieval Latin ultramarinus. The name is said to describe the journey rather than the colour, because the stone it was made from reached Europe by ship from Asia.

Which pharaoh's funeral mask is inlaid with the blue stone from which ultramarine was later made?

Tutankhamun. The stone rims the eyes and eyebrows of his gold mask, and it had been traded all the way from mines in what is now Afghanistan.

Prussian blue, the first modern synthetic pigment, is the traditional 'blue' in what?

Blueprints. The copying paper turns Prussian blue wherever light strikes it, so the lines of the drawing, which block the light, stay white on a blue sheet.

Which artist's Blue Period, from 1901 to 1904, followed the suicide of his friend Carles Casagemas?

Pablo Picasso. He was so short of money in those years that he painted over used canvases, which is why scans keep finding hidden pictures beneath his Blue Period works.

Blue eyes have no blue pigment: their irises are just low in which other pigment?

Melanin. Blue-eyed people share a genetic switch that turns down production of the brown pigment in the front of the iris, so the blue is an effect of light rather than a dye.

The blue whale is the largest animal ever known: roughly how much can the biggest weigh?

About 200 tonnes. Whalers after its oil drove the species to the brink of extinction in the 20th century, until an international ban in 1966 protected it.

A blue whale's diet consists almost entirely of what?

Krill. The largest animal ever known lives on tiny shrimp-like creatures, gulping a huge mouthful of sea and then straining the water out through its baleen plates.

A blue whale's heart can slow to just two beats a minute when the animal does what?

Dives deep to feed. The slow beat stretches the whale's oxygen supply underwater, and once it is back at the surface its heart races at up to 37 beats a minute.

The blue-ringed octopus carries tetrodotoxin, the same nerve poison found in which fish?

Pufferfish. The octopus does not make the poison itself: bacteria living in its salivary glands produce it, and its rings flash bright blue as a warning only when it feels threatened.

About half of all breeding pairs of blue-footed boobies nest on which islands?

The Galápagos. Males court with a high-stepping strut that shows off their feet, and the bluer the feet, the better a male's chances with a female.

The clever, acorn-hoarding blue jay belongs to which family of birds?

The crow family. Like other members it is a talented mimic, and a blue jay can copy a hawk's scream well enough that it may frighten other birds away from their food.

Under the popular definition, when is a full moon called 'blue'?

It is the second in one calendar month. The rule began as a slip, when a 1946 magazine article misread an old farmers' almanac, and a radio show and Trivial Pursuit later spread it.

After which 1883 volcanic eruption did the Moon really look blue for months?

Krakatoa. Its ash filled the upper air with particles just the right size to filter out red light, so the Moon shone blue, and sometimes green, through the haze.

Bluetooth technology is named after a 10th-century king of which country?

Denmark. The king's nickname was only meant as a placeholder: the names lined up to replace it, RadioWire and PAN, fell through before launch, so the codename stuck.

Bluetooth is named after a medieval king who was famed for doing what?

Uniting Scandinavian lands. Intel engineer Jim Kardach proposed the name because the new radio link was meant to unite the PC and mobile phone industries in the same way.

The Bluetooth logo is made by merging two what?

Norse runes. They are Hagall and Bjarkan, the initials of the king the technology is named after, who is said to have earned his nickname from a dead tooth that looked dark blue.

The 1873 patent that gave birth to blue jeans protected which feature?

Copper rivets. Reno tailor Jacob Davis used them to stop the pockets of work trousers tearing, then asked Levi Strauss, who sold him the cloth, to share the patent.

Until factories began making it in the 1890s, where did the world's indigo dye come from?

Plants. Indigofera shrubs supplied most of the dye until factory-made indigo went on sale in the late 1890s, and within two decades the plant trade had all but collapsed.

By legend, which blue cheese was born when a shepherd left his lunch in a cave to chase a girl?

Roquefort. In the tale he came back months later to find his cheese veined with blue mould, and the real thing is still ripened in the caves of Roquefort-sur-Soulzon.

The 'blue chip' stock term comes from which game, where blue chips are traditionally worth most?

Poker. Dow Jones lore credits an employee, Oliver Gingold, with borrowing the gambler's term in the 1920s after watching shares change hands at $200 or more.

'Blue blood' translates a boast that old Iberian noble families made in which language?

Spanish. The phrase is sangre azul, claimed by old families of Castile, and the idea was probably that fair-skinned nobles could point to the blue veins showing through their skin.

London's blue plaques honour notable people, but only once the person has been what?

Dead for 20 years. The wait is meant to give the judges hindsight, though the oldest surviving plaque breaks the rule: it went up in 1867 to Napoleon III, who was still alive.

The BBC children's show Blue Peter is named after a flag that ships fly when about to do what?

Leave port. The name was chosen to cast the programme as a ship setting out on a voyage of adventure, with new things for its young viewers to discover along the way.

The sleeve of New Order's 1983 single 'Blue Monday' was designed to look like what?

A floppy disk. Designer Peter Saville had just seen one for the first time, and the die-cut copy was so costly that, as the story goes, Factory Records lost money on every single sold.

Which Italian group had a worldwide hit in 1999 with 'Blue (Da Ba Dee)'?

Eiffel 65. The name was half an accident: 'Eiffel' came off a ready-made list of band names, and the 65 was two digits of a phone number jotted across the single's label copy.

The Blue Note label, launched in 1939 by an emigrant from Berlin, is celebrated for which kind of music?

Jazz. Co-founder Alfred Lion fell for the music as a boy in Berlin, and the session photographs taken by his childhood friend Francis Wolff ended up on the label's album covers, setting a trend.

Which 1959 Miles Davis album is often called the greatest record of its genre?

Kind of Blue. Rather than written-out tunes, Davis gave his players little more than sketches of scales to improvise on and called almost no rehearsal before the tapes rolled.

In which city did Blue Man Group get its start in the late 1980s?

New York. The group's first outing was a mock funeral for the 1980s in Central Park, coffin and Rambo doll included, staged in the hope that MTV would cover it, which it did.

Which technology company is nicknamed 'Big Blue'?

IBM. The nickname is echoed in its chess computer Deep Blue, which in 1997 became the first machine to beat a reigning world champion, Garry Kasparov, in a match.

Which version of Windows swapped the famous 'blue screen of death' for a black one?

Windows 11. The black screen came in a 2025 update, part of a push to make Windows sturdier after a faulty CrowdStrike update left millions of PCs stuck on blue screens the year before.

Which Blue Öyster Cult song is a classic-rock staple famous for its cowbell?

(Don't Fear) The Reaper. A 2000 Saturday Night Live sketch, with Christopher Walken as a producer demanding 'more cowbell', turned a background percussion part into the song's trademark.

The Blue Nile and the White Nile meet to form the Nile at which capital city?

Khartoum. There the Blue Nile, down from the Ethiopian highlands, joins the White Nile, and it is the Blue that supplies most of the great river's summer floodwater.

The Blue Angels flight display team belongs to which branch of the US military?

The Navy. Admiral Chester Nimitz ordered the team formed in 1946, the year after the war ended, to keep the public interested in naval aviation and to lift morale in the service.

Iceland's Blue Lagoon gets its milky blue colour from a high content of what?

Silica. The lagoon is an accident of industry: it formed in the 1970s from the mineral-rich water discharged by the Svartsengi geothermal power station, and locals began bathing in it.

The Blue Grotto, a glowing sea cave, lies on the coast of which Italian island?

Capri. Sunlight entering through the water beneath the entrance lights the cave, which the Romans knew and which two German visitors rediscovered for the wider world in 1826.

Newborn Blue Ivy Carter became the youngest person ever on a Billboard chart via which 2012 Jay-Z song?

Glory. Jay-Z recorded his daughter's breathing, cries and coos and released the track within two days of her birth, crediting the newborn as B.I.C.

Blue Origin, founded in 2000 by Jeff Bezos, is headquartered in which state?

Washington. The company is based in Kent, just outside Seattle, where Bezos built Amazon, even though its rockets lift off far away, from West Texas and Florida.

Which national football team is nicknamed Les Bleus?

France. Their blue comes from the tricolour, but Italy's does not: the Azzurri play in the colour of the House of Savoy, the old royal dynasty, and the Italian flag has no blue at all.

For what invention did Nakamura, Amano and Akasaki share the 2014 Nobel Prize in Physics?

The efficient blue LED. Red and green LEDs had existed for decades, but white light needs blue as well, so the trio's breakthrough is what made bright, low-energy LED lamps possible.

Isaac Newton named seven spectrum colours, including blue, to match the number of what?

Notes in the musical scale. Newton believed colours, like notes, formed harmonies, so he stretched his first, shorter list, adding indigo, until the spectrum had the seven steps of an octave.

Denim, the cloth of blue jeans, is said to take its name from which French city?

Nîmes. The cloth was sold as serge de Nîmes, and its partner word has the same kind of story: 'jean' is short for the fustian of Genoa.

Which Dutch city gave its name to the blue-and-white pottery made there to imitate Chinese porcelain?

Delft. Its potters could not make true porcelain, so when shipments from China dried up in the 1600s they copied the blue-and-white look in tin-glazed earthenware.

Who wrote and first recorded 'Blue Suede Shoes', months before Elvis Presley's famous cover?

Carl Perkins. A car crash on the way to perform it on national television put him in hospital, and while he recovered Elvis Presley had a hit with his own version.

Saint-Denis near Paris, rebuilt from the 1130s with deep blue stained glass, is seen as the first church in which style?

Gothic. Abbot Suger opened up its walls for great windows, and the deep cobalt blue made in his glass workshops was soon copied at Chartres Cathedral.

Which American composer wrote 'Rhapsody in Blue' for a 1924 concert billed as an experiment in modern music?

George Gershwin. With only five weeks until the premiere he had to hurry, and he later said the whole shape of the piece came to him on a rattling train to Boston.