100 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.

Sonic the Hedgehog was coloured blue to match the logo of which video game company?

Sega gave Sonic the deep blue of its own logo, while the design of his shoes was inspired by Michael Jackson's boots and by Santa Claus.

Blue curaçao liqueur, despite its electric colour, is flavoured with the dried peel of which fruit?

Bitter oranges called laraha, grown on the Caribbean island of Curaçao, give the liqueur its taste. The spirit is naturally colourless, and the blue is simply added dye.

On which planet does the sky around the setting Sun turn blue while the daytime sky is butterscotch?

Mars reverses Earth's colours because its thin air is full of fine dust, which scatters light differently and leaves a cool blue glow around the setting Sun.

The blue mascot in Twitter's logo until 2023 was named in honour of which Boston Celtics legend?

Larry Bird inspired the pun: the little blue songbird in the logo was named Larry the Bird.

Blue zones, named after villages circled on a map in blue pen, are regions famed for what?

Exceptionally long lives, often past 100, are claimed for places such as Okinawa and Sardinia. Later research has cast doubt on some of the claims.

In the United States, old 'blue laws' restrict shopping and alcohol sales on which day of the week?

Sunday was kept free for worship under these rules, and nobody knows where the name comes from. One popular tale says Connecticut printed its early laws on blue paper.

The Smurfs, the blue creatures created by cartoonist Peyo, come from the comics of which country?

Belgium gave the world the Smurfs in 1958 as Les Schtroumpfs, a word Peyo said he invented over a meal when he could not remember the word for salt.

Blu-ray discs, which hold far more than DVDs, are named for the colour of which part of a player?

The laser that reads the disc is blue, and its shorter wavelength lets data be packed far more densely than the red laser of a DVD player allows.

Bigleaf hydrangea flowers turn blue rather than pink when the shrub grows in soil that is what?

Acidic soil lets the roots take up aluminium, and the metal shifts the flower pigment toward blue. In alkaline ground the very same shrub blooms pink.

Which spacecraft took the 'Pale Blue Dot' photo of Earth from six billion kilometres away in 1990?

Voyager 1 turned its camera homeward at Carl Sagan's urging, and Earth shows up as a speck less than a pixel wide, caught in a band of sunlight reflected by the camera.

In James Cameron's Avatar, the tall blue-skinned Na'vi live on which lush moon mined for unobtanium?

Pandora orbits in the Alpha Centauri system, and James Cameron has said one reason he made its people blue was to connect them to Hindu deities.

In which 1999 film is the hero offered a blue pill to stay in a comfortable illusion?

The Matrix has the rebel leader Morpheus offer Neo two pills, and choosing the red one, which reveals the unsettling truth, has since become an everyday metaphor.

In Doctor Who, a fault leaves the time machine TARDIS stuck in the shape of a blue what?

Police box kiosks, a kind of telephone booth, were once a common sight on British streets, and the ship's broken chameleon circuit keeps it in that disguise.

In Pixar's Inside Out, which of Riley's five emotions is the blue one, voiced by Phyllis Smith?

Sadness spends much of the story being kept away from the controls by Joy, yet she proves to be the emotion that lets Riley ask others for help.

Which animated Pixar character is a regal blue tang, a reef fish of the Indo-Pacific?

Dory can read human writing and speak whale despite her short-term memory loss, and a 2016 sequel named after her finally gave her parents and a past.

In the series Blue's Clues, what does the puppy Blue leave on objects to mark them as clues?

A paw print marks every clue she leaves for the host and the viewers to puzzle over, and "she" is right: the blue puppy of the title is a girl.

Bluey, the hit cartoon about a Blue Heeler puppy and her family, is set in which Australian city?

Brisbane, the Queensland capital, inspired the cartoon's sunny settings. A Blue Heeler is an Australian Cattle Dog, nicknamed for nipping at the heels of reluctant cattle.

Which blue-skinned X-Men shapeshifter was played on film by Rebecca Romijn and Jennifer Lawrence?

Mystique can mimic the looks and voice of anyone she meets, and in the comics she is the adoptive mother of the X-Men heroine Rogue.

In which animated Beatles film do the music-hating Blue Meanies invade the paradise of Pepperland?

Yellow Submarine sends cartoon Beatles to free Pepperland with songs, but actors supplied their speaking voices and the real band appears only in the closing scene.

The Blue Fairy who helps Pinocchio is known in Carlo Collodi's original 1883 book for which feature?

Her turquoise hair gives her the book's own name for her, the Fairy with Turquoise Hair, and she keeps reappearing to scold the wooden puppet out of bad behaviour.

The Sultan Ahmed Mosque, nicknamed the Blue Mosque for the tiles inside it, stands in which city?

Istanbul's great Ottoman mosque is lined with thousands of Iznik tiles painted mostly in blue, and it is flanked by six minarets.

Chefchaouen, a mountain town nicknamed the Blue City for its painted houses, is in which country?

Morocco also calls the town its Blue Pearl, and the old quarter is a maze of lanes and traditional houses painted in blue and white.

Which Canadian city's Blue Jays were the first team from outside the US to win the World Series?

Toronto took the title in 1992, only the club's 16th season, and then won it again the following year.

In the annual Boat Race on the River Thames, which university's crew rows in light blue?

Cambridge races in light blue and Oxford in dark blue, and by tradition the members of both crews are themselves known as Blues.

In Formula One, a waved blue flag tells someone about to be lapped to do what?

Let the driver behind pass is the order, and it has teeth: a driver who ignores three waved blue flags in a row can be penalised by the stewards.

Blue Mountain coffee, prized for its mild taste and low bitterness, grows on which Caribbean island?

Jamaica protects the name: only beans certified as grown in its cool, misty Blue Mountains, which rise above 2,200 metres, may be sold under it.

The Great Blue Hole, a marine sinkhole made famous by Jacques Cousteau, lies off which country?

Belize owes the site's fame to Cousteau, who sailed his ship Calypso there in 1971 to chart its depths and ranked it among the world's top five dive sites.

The Blue Ridge Mountains, hazy blue from a gas their trees release, belong to which larger range?

The Appalachians include the Blue Ridge, whose forests release isoprene into the air and so create the haze that gives the mountains their colour and their name.

Which supposedly cursed blue gem did jeweller Harry Winston donate to the Smithsonian in 1958?

The Hope Diamond gets its deep blue from traces of boron, and it glows red after exposure to ultraviolet light, an eerie trick that may have fed the legend.

The Kelley Blue Book, first issued by a California dealer in 1926, is a guide to the value of what?

Cars have been priced by the guide since Les Kelley, a dealer who started out with three Model T Fords, first published it. It was also the first to use mileage to set a value.

Which sea creature's bright blue blood is harvested to test medicines for bacterial toxins?

Horseshoe crab blood yields an extract that detects bacterial toxins, which makes it a standard safety test, and the animal is closer kin to spiders than to true crabs.

Which gas in the atmospheres of Uranus and Neptune absorbs red light, tinting both planets blue?

Methane soaks up the red end of sunlight, so what bounces back looks blue-green, and a thicker layer of haze makes Uranus the paler of the two.

Blue light from screens at night suppresses which hormone that readies the body for sleep?

Melatonin is made by the pineal gland once light fades, bringing on drowsiness, and wavelengths of about 460 to 480 nanometres are the ones that shut it down hardest.

Which 1972 Moon mission's crew took 'The Blue Marble', one of history's most reproduced photographs?

Apollo 17 was on its way to the Moon when an astronaut took the shot from about 29,000 km away, and the original frame shows the South Pole at the top.

Blue supergiant Rigel and red supergiant Betelgeuse are the brightest stars in which constellation?

Orion's Rigel carries the label Beta, usually given to a constellation's second-brightest star, yet it almost always outshines Alpha, the variable Betelgeuse.

What is the name of the eerie blue glow seen in the water around an underwater nuclear reactor core?

Cherenkov radiation appears when charged particles cross water faster than light itself can travel through it, and working out the effect earned a 1958 Nobel Prize.

The Andromeda Galaxy's light is blueshifted, which tells astronomers that the galaxy is doing what?

Moving toward us squeezes a galaxy's light to shorter, bluer wavelengths, a shift that Vesto Slipher first found for Andromeda with observations begun in 1912.

The blue dragon, a tiny sea slug, steals stinging cells from which venomous drifter that it eats?

Portuguese man o' war stings end up stored in the slug's own tissues as a defence, so picking one up can hurt a person as much as touching its prey.

Which metal, the source of a famous deep blue pigment, takes its name from a German word for goblin?

Cobalt recalls the kobold, a goblin that German silver miners are said to have blamed for a troublesome ore that spoiled their smelting and made them ill.

Which major language has no single word for blue, only separate words for light blue and dark blue?

Russian speakers say goluboy for a pale sky blue and siniy for a darker shade, and they have no umbrella word that covers both.

Which composer wrote The Blue Danube, a waltz first sung in 1867 by a Vienna men's choir?

Johann Strauss II saw the premiere judged only a mild success, and he is reputed to have cursed the waltz that became one of the best-loved pieces in classical music.

What name did blues legend B.B. King give his guitars after rescuing one from a burning dance hall?

Lucille was the woman two men were fighting over when they knocked over a barrel of burning kerosene in 1949, and King kept the name as a reminder never to run into a fire again.

Which Delta blues guitarist, who died at 27, is said to have sold his soul at a crossroads?

Robert Johnson recorded just 29 songs, at two sessions in Texas in 1936 and 1937, yet they went on to shape generations of blues and rock musicians.

The Blues Brothers, Jake and Elwood, began as a musical act on which American television show?

Saturday Night Live cast members Dan Aykroyd and John Belushi debuted the act in April 1978, on an episode hosted by the comedian Steve Martin.

The NHL's St. Louis Blues are named after a 1914 song by which self-styled 'Father of the Blues'?

W. C. Handy did not invent the blues, but he was among the first to publish it as sheet music, which carried a regional Delta style to a far wider audience.

Which French artist developed his own signature deep blue for a series of single-colour canvases?

Yves Klein's International Klein Blue came from work with a Paris paint supplier on a resin binder that lets the powdery pigment keep its raw intensity on canvas.

Which English artist painted The Blue Boy, seen by 90,000 Londoners before it left for California?

Thomas Gainsborough dressed his sitter in 17th-century costume as a homage to Anthony van Dyck, and the portrait returned to London on loan a century to the day after it left.

Which Saharan people are nicknamed the 'Blue People' because their dyed veils can stain the skin?

The Tuareg nickname comes from the indigo cloth of the tagelmust, a veil that by tradition is worn by the men and not by the women.

Which French author published Bluebeard, the tale of a rich man who murders his wives, in 1697?

Charles Perrault printed the grim tale in the same 1697 collection that held his versions of Cinderella, The Sleeping Beauty and Little Red Riding Hood.

The Blue Riband was an unofficial prize for the passenger liner that did what at the highest speed?

A liner that crossed the Atlantic at a record average speed took the title, and no passenger liner has bettered the mark that United States set on her maiden voyage in 1952.