50 Fun Facts About Color

In the mnemonic ROYGBIV for the colours of the rainbow, what does the I stand for?

British schoolchildren learn the same order as 'Richard Of York Gave Battle In Vain', a nod to the Duke of York's death at the Battle of Wakefield in 1460.

Newton first split the spectrum into five colours. Why did he later add two more to make seven?

Newton was also the first person to use the word 'spectrum' in print for the band of colours, in 1671.

Which colour of visible light has the longest wavelength?

The human eye responds to wavelengths from roughly 380 to 750 nanometres, and this colour sits at the top of that range.

The daytime sky is blue because of what physical effect, named after a British physicist?

Lord Rayleigh's 1871 explanation is a textbook example of solving a physics problem by dimensional analysis alone.

In the CMYK printing model, what does the K stand for?

The black plate was the 'key' plate that the other three colour plates were aligned to.

How many types of colour-sensing cone cell does a typical human retina have?

You have only about six or seven million cones, versus roughly 92 million rods that see in low light but not in colour.

Which animal's eyes contain 12 to 16 types of photoreceptor cell and can detect circularly polarised light?

Despite all that hardware, tests suggest they are surprisingly poor at telling similar hues apart; their eyes seem built for speed, not subtlety.

Which is the most common form of colour blindness in humans?

The genes involved sit on the X chromosome, so it shows up in around 1 in 12 men but only about 1 in 200 women.

Colour blindness is sometimes called 'daltonism' after which English chemist?

DNA analysis of his preserved eye tissue in 1995 confirmed he was a deuteranope, lacking working green-sensitive cones.

Blue eyes contain no blue pigment. Their colour comes from the same effect that makes what else blue?

Roughly 79% of the world's population has brown eyes, and every blue-eyed person is thought to descend from a single ancestral mutation.

Which pigment, with brown-black and red-yellow forms, is the primary determinant of human skin colour?

Ginger hair is a small amount of the dark form mixed with plenty of the red-yellow form, pheomelanin.

Chlorophyll makes leaves green by absorbing light most strongly in which two colours?

The molecule holds a magnesium atom at its centre, where the structurally similar haem in your blood holds iron.

Magenta is described as an 'extra-spectral' colour. What does that mean?

Your brain invents it when red-sensitive and blue-sensitive cones fire together with the green ones quiet, closing the colour wheel into a loop.

Tyrian purple, the dye reserved for Roman emperors, was extracted from what?

Twelve thousand Murex brandaris snails yielded about 1.4 grams of dye, enough to colour just the trim of one garment.

In 1856, William Henry Perkin discovered the dye mauveine while trying to make what?

The failed malaria-drug experiment left a purple residue in his flask, and the colour was so popular from 1859 to 1861 that the era is nicknamed the 'mauve decade'.

Renaissance ultramarine was ground from lapis lazuli mined mainly in which modern country?

Its name means 'beyond the sea', and it was so precious that artists saved it almost exclusively for the robes of the Virgin Mary.

A Bihar-made painters' pigment named for its country of origin reportedly came from the urine of cows fed on what?

The cattle were reportedly kept malnourished on the diet, and the process was allegedly outlawed as inhumane in 1908, though no record of that law has ever been found.

The red dye carmine, still used in food and cosmetics, is made from which creature?

It takes about 70,000 cochineal insects to make a single pound of dye, and in colonial Latin America it was the second most valuable export after silver.

'Mummy brown', a pigment sold to artists into the 20th century, was made from what?

When Edward Burne-Jones learned in 1881 what was in his tube, he insisted on giving it a decent burial in his garden.

Prussian blue, the first modern synthetic pigment, was made by accident around 1706 in which city?

Taken orally, the same compound is a WHO essential medicine, used as an antidote to thallium and radioactive caesium poisoning.

Scheele's green, a popular Victorian pigment, was dangerous because it contained which element?

Napoleon's rooms on St Helena were painted in his favourite green, which fuelled a long-running poisoning theory that later research rejected in favour of stomach cancer.

The word for the dye that colours blue jeans comes from a Greek word meaning what?

The plant-based dye was largely replaced after BASF industrialised a synthetic version in 1897, building on Adolf von Baeyer's chemistry.

Which French artist registered his signature ultramarine paint, known as IKB, in 1960?

The trick was not the pigment but the binder, a synthetic resin that let the ultramarine keep its raw powdery intensity once dry.

Vantablack, one of the darkest substances ever made, absorbs up to 99.965% of visible light using what?

Surrey NanoSystems handed the artist Anish Kapoor exclusive rights to use it in art, which triggered a memorable feud with the rest of the art world.

YInMn Blue, found by accident at Oregon State in 2009, is named for yttrium, indium and which third element?

Crayola's 2017 crayon 'Bluetiful' was inspired by it, though the actual crayon contains none of the pigment.

Picasso's Blue Period, from 1901 to 1904, was directly followed by which of his periods?

Picasso said he started painting in blue after learning of his friend Carlos Casagemas's suicide, though he was not in Paris when it happened.

The name Crayola was coined by Alice Binney from 'ola', for oily, and 'craie', the French word for what?

The company sold crayons as Binney & Smith for over a century before renaming itself Crayola LLC in 2007.

Crayola's 'Peach' crayon carried what name for most of the years between 1903 and 1962?

The same crayon was briefly called Pink Beige in the late 1950s before the company settled on the fruit.

Which sky-blue shade was Pantone's very first Color of the Year, for 2000?

The company hyped it as the 'colour of the millennium'; the only year with two winners was 2016, when Rose Quartz shared the title with Serenity.

Which warm brown shade did Pantone name its Color of the Year for 2025?

It followed the soft orange Peach Fuzz of 2024, and was in turn succeeded by the near-white Cloud Dancer for 2026.

Since Mauritania's 2017 flag change, which is the only sovereign country whose flag has no red, white or blue?

The flag is a gold saltire on black and green, colours that in the original design stood for hardships, the land, and the sun.

Which country flew the world's only single-colour national flag, plain green, from 1977 to 2011?

The only interruption to its record was 1996–97, when Afghanistan under the Taliban briefly used an all-white flag.

The Pan-African colours of green, yellow and red were borrowed from which country's flag?

The inspiration was Ethiopia's independence: it defeated an Italian army at Adwa in 1896 and stayed outside European control through the colonial era.

Which 19th-century British prime minister first noticed Homer never uses a word for 'blue'?

The phrase 'wine-dark sea' appears five times in the Iliad and twelve in the Odyssey; Gladstone argued Homer sorted colours by brightness rather than hue.

Japan's 'go' light is called 'ao', a word traditionally covering green and which other colour?

In 1973 officials decreed the go light should be the bluest legal shade of green, so the colour would match the name without breaking the international convention.

The earliest known use of "orange" as a colour in English, in 1502, described clothing bought for which royal?

Before the fruit lent its name, Old English speakers made do with geoluread, literally 'yellow-red'.

Which shade of pink, 'drunk-tank pink', has been painted in prison cells to calm aggression?

Iowa football coach Hayden Fry had the visitors' locker room at Kinnick Stadium painted the colour to make opponents passive; a 2014 study found it made no difference.

What paint scheme did the US Navy suggest for the Golden Gate Bridge instead of 'international orange'?

Consulting architect Irving Morrow picked the orange vermilion himself, arguing it suited the surroundings and showed up in fog.

An aircraft's 'black box' flight recorder is actually required to be painted what colour?

The point is to make it easy to spot in wreckage; the 'black box' name stuck anyway.

Flamingos are born greyish. What turns adults pink?

A pale flamingo is usually an unhealthy or malnourished one, which is why zoos have to dose their diets carefully.

Why does a bull charge a matador's red cape?

Like most mammals, cattle are red–green colour blind, so the cape's colour is for the audience, not the animal.

Chameleons change colour most commonly for what reason?

A 2015 study showed they do it by actively adjusting the spacing of guanine nanocrystals in their skin, tuning which wavelengths reflect.

A polar bear's fur looks white, but what colour is its skin?

The guard hairs are transparent and hollow, so the 'white' is scattered light with no pigment at all, and bears yellow with sun exposure until they moult.

Which explanation for zebra stripes is the most strongly supported by evidence?

Horses dressed in zebra-print coats got fewer fly landings too, and underneath the stripes a zebra's skin is black.

The vivid blues on peacock feathers and Morpho butterfly wings are produced not by pigment but by what?

Robert Hooke spotted this under his microscope in 1665, and Newton explained it in Opticks in 1704.

The idiom 'blue blood' for aristocracy is a translation of 'sangre azul' from which language?

Old Castilian nobles supposedly proved their pedigree by holding up a pale arm to show the blue veins beneath, in contrast to the darker-skinned Moors.

The 'red herring' of detective fiction was originally a real food. What was it?

William Cobbett popularised the metaphor in 1807 with a story about dragging one across a hare's trail to throw the hounds off the scent.

The popular 'second full moon in a month' definition of a blue moon traces to a 1946 misreading in which magazine?

Amateur astronomer James Hugh Pruett misread the 1937 Maine Farmers' Almanac, whose own definition was the third full moon in a season that has four.

'The Dress' of February 2015 looked white and gold to many. What colours was it really?

The retailer, Roman Originals, saw a sales surge and made a one-off white-and-gold version for charity.

Frank Cyr standardised school-bus yellow at a 1939 conference held at which institution?

The shade was chosen because black lettering on it stayed legible in semi-darkness, and Cyr is remembered as the 'Father of the Yellow School Bus'.