A magnificent pair of late 19th century sapphire and diamond earrings A fancy grayish blue diamond ring, by Andrew Grima,

It's the world's favourite colour, found in the rarest diamonds and in depictions of the Virgin Mary – and yet some cultures still don't have a word for it, says James Fox

Why make so much of fragmentary blue
In here and there a bird, or butterfly,
Or flower, or wearing-stone, or open eye,
When heaven presents in sheets the solid hue?

Fragmentary Blue
Robert Frost

Blue, as Robert Frost understood, is an elusive colour. Unlike most other hues, it rarely takes on a tangible form in nature. Apart from sapphires and blue diamonds, there are few naturally occurring blue things on the Earth. The colour accounts for less than four per cent of plants, five per cent of flowers and eight per cent of fruits. And though there seem to be several blue-looking birds and fish out there, only two of the planet's 64,000 vertebrate species possess genuine blue pigment.

What's more, the blues that do exist in our world are extremely difficult to pin down. Indeed, blue only thrives in the distant realms of sea, sky and horizon. And while those vast cerulean provinces often surround us on every side, their bashful colour stays stubbornly out of reach. Because in the end, we can't touch the blueness of the sky; we can't bottle the blueness of the sea; and no matter how far we travel, we'll never reach the blue horizon.

An exception, however, comes in the form of precious stones. Blue diamonds are exceptionally rare, so when they do come on the market, they command substantial prices. In 2013, a rare 5.30 carat fancy deep-blue 'trombino' diamond ring, by Bulgari, circa 1965, sold for a record-breaking £6.2m ($9.5m). The latest example – a rare greyish-blue diamond set in a ring and surrounded by blue sapphires and diamonds, made by jewellery designer Andrew Grima – is to be offered at Bonhams in London in December.

Blue's perennial absence from our lives has had far-reaching consequences. It is one of the reasons why it took humans so long to give the colour a name. There are virtually no references to the hue in all of ancient literature. Take Homer, for instance. His famous 'wine-dark' seas were only 'wine-dark' because the Ancient Greeks hadn't yet invented a word for blue. And today there remain several languages around the world that still don't have a term for the colour.

But it wasn't just absent from language. The colour's natural scarcity made blue pigments so difficult to produce that they were largely absent from the first 20,000 years of art. It was only at the end of the Neolithic period when the first blues were invented. In Asia, the leaves of indigo and woad plants were fermented to produce deep blue dyes; in the Middle East, the secretion of a sea snail was transformed into a beautiful cerulean; and in about 2550BC, the ancient Egyptians developed their eponymous Egyptian blue, which continued to be used for thousands of years.

Of course, the greatest blue pigment came from a stone called lapis lazuli. But this too was extremely rare. For centuries, it could only be found in one small mine in the remote mountains of Afghanistan. Yet what a stone it was. In its raw state, lapis lazuli uncannily resembles a fragment of the firmament: its lazurite blue phosphoresces like a darkening sky; white calcite races across its surfaces like cirrocumulus clouds; and specks of golden pyrite sparkle like celestial constellations.

Europeans were convinced that the celestial stone had miraculous properties. They used lapis lazuli to heal warts and ulcers; to manage menstruation and urinary tract infections; and to treat fevers, cataracts and depression. It rarely worked. But in one field its abilities were beyond doubt: for lapis lazuli was the sole source of an exceptional blue pigment that the Venetians called azzurro oltramarino – ultramarine. The name itself referred to the colour's exotic origins; in Italian, oltremare means 'overseas'.

Ultramarine did not come cheap; it cost up to a hundred times more than most other pigments on the market, and was often more expensive than gold. And so it naturally came to be reserved for the most sacred things. From the 12th century onwards only the Virgin Mary was consistently shown in ultramarine robes. In Sassoferrato's Virgin Mary in Prayer of 1650, in the National Gallery in London, the colour is so overpowering that one barely even notices the Virgin who wears it.

This was the beginning of the long and enduring connection between Catholicism and blue. Indeed, it's probably because of ultramarine that Hercule Poirot's famous profanity was 'sacré-bleu' and not sacre-any-other-colour.

Yet blue wasn't always heavenly. In the 19th century, the colour was increasingly associated with the dark side of the world. English speakers linked it to commotions ('blue murder'), obscenity ('blue talk'), inebriation ('blue drunk'), despair ('blue funk'), terror ('blue fear'), and markers of diabolical presences ('blue fire'). By the 1900s the colour's angst-ridden associations were even expressed in the melancholic African-American music that came to be known as 'the Blues'.

Blue's darker associations peaked in the early 20th century. In his famous 'blue period', which was provoked by the suicide of his best friend Carlos Casagemas, Pablo Picasso used the rancid hues of synthetic blue pigments to capture a mood of cold, dark and hopeless despair. The blues that surround his Melancholy Woman (1902) hide in the shadows behind her and eat into her flesh like frostbite. The poor protagonist seems to be suffocating in foetid air or drowning in dirty seas.

Others, however, saw in blue a set of huge emotional opportunities. Wassily Kandinsky, who didn't just see blue but could also hear it, wrote that the colour "called man toward the infinite, awakening in him a desire for the pure and, finally, for the supernatural". In a lovely painting from 1903, The Blue Rider, Kandinsky depicted himself as an intrepid blue-cloaked explorer, galloping across a verdant hill towards an ultramarine horizon.

No artist loved blue more than the French artist Yves Klein. Born in 1928, Yves Klein spent his summers on France's felicitously named Côte d'Azur and became obsessed with its Mediterranean blues. One day when he was about 18 years old, Klein stretched out on the beach, raised his right hand into the air and signed his nine-letter name across the firmament. It was a prophetic gesture of ambition, for Klein spent the remainder of his life attempting to conquer this most unconquerable of colours.

Believe it or not, Klein succeeded. In 1959, he invented his very own blue, which he patented under the name 'International Klein Blue'. It is to my mind the greatest blue ever made, far superior even than traditional ultramarine, and his IKB monochromes are so resonant that they cause their viewers' retinas to vibrate. Over the next few years, Klein applied his pigment to everything: paintings, screens, sponges, tapestries and naked women. At his wedding he even added it to the cocktails and so turned his guests' urine International Klein Blue.

In some ways we are all like Yves Klein, because all of us love blue. In 2004, a survey of 13,000 people found that blue was the most popular colour in every country in the world. More remarkable was the extent of its superiority. In Germany, where a staggering 47 per cent of people declared blue to be their favourite, it was four times more popular than second-placed red. And even in the nation where it was least successful, Russia, blue still received a third of the vote.

Blue's dominance can now be seen everywhere. It's the colour of choice for international organisations such as the United Nations and European Union; it dominates the logos of the world's blue-chip corporations; and according to some estimates, at any point in time half of the world's entire population (some 3.5 billion people) are believed to be wearing blue jeans.

Blue has conquered our blue planet. But the real reason we love the colour so much, and the reason we've coveted it for centuries, is that deep down we know we can't have it.

James Fox is an art historian and broadcaster, whose television programmes include A History of Art in Three Colours.

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