Custard yellow, sky blue, pea green...

Can colour ever be entirely decoupled from life? A fascinating show explores the ways in which artists have tried to do just that

French artist Sophie Calle once asked a group of blind people to describe their idea of beauty. One of the given answers was a colour. "Green is beautiful," said a young woman, "because every time I like something I'm told it's green. Grass is green, trees, leaves and nature too. I like to dress in green."

What generous logic: green must be beautiful because it equals nature. But consider some of its particular shades - bottle green, arsenical green, screaming green, olive drab - and it is clear that associations can easily imprison a colour. Artists, what is more, who might be expected to have an open-minded attitude, are often especially dogmatic. Van Gogh insisted that yellow was the colour of hope, Kandinsky that blue represented the transcendent infinite. Mondrian loathed green precisely because of nature.

The idea of colour having no connotations whatsoever is, in fact, relatively new for art. Around 1950 is where this show pins it, beginning with Ellsworth Kelly's Spectrum Colors Arranged by Chance, an enormous grid of coloured squares assembled in no obvious order or pattern that very obviously invokes the colour chart.

Colour charts - from Pantone to Winsor & Newton - are association-free. They represent colour in splendid isolation, expressing nothing other than the essence of itself and a flat shade in ink or pigment. Who doesn't love these little samples, pure, abundant, uninflected? They are an obvious gift for the conceptual artist, a means of asking questions about colour, meaning, art's relationship with life. But who would have thought quite so many artists would have made works that actually look like colour charts?

Gerhard Richter's permutations of coloured squares (which conspicuously resemble Kelly's), Jim Dine's rectangles, Jennifer Bartlett's pixellated grids, Angela Bulloch's light boxes flashing up the Apple Mac palette, Richard Serra's film of his own hand flipping through a colour book with a certain aggression, as if throwing it all away (he subsequently gave up painting for sculpture): there is almost too much to take in.

And pretty soon you start to rebel, noticing all the ways in which these works cannot remain high-mindedly theoretical. The blurry blue and white stripes in Michel Parmentier's painting are so nautical they conjure deckchairs, sailors and oceans in an instant, no matter what he says. Andy Warhol's electric chair is inevitably more or less horrifying depending on whether it appears silk-screened in blood red or blue.

Blinky Palermo's swatches of green, grey and blue cloth have long since become his true colours, as much a signature as Daniel Buren's stripes which, not incidentally, cannot help being awning, deckchair, wrapping paper or gondolier stripes according to their particular colour and hue.

It is all very well to arrange colours in arbitrary permutations - generated by a computer, say, or by mathematical progressions of randomly distributed numbers - but still they have to be presented in some form or other. Stripes, oblongs, squares or dots of pigments on canvas inevitably become abstract paintings, no matter that the artist may be completely at odds with that modern tradition; enamelled panels cannot help evoking car body parts. When Jim Lambie covers the floor with brilliantly coloured striations of sticky tape that go with the flow of every corner and threshold, the effect is op-art dazzle, dynamic pulsation, but also a vision of disco carpet.

Art's colours cannot sidestep history or form. And though the curators of this show, which originated at Moma in New York, have produced a superbly intelligent catalogue setting out their reflections and arguments on colour as a radical free zone, it is hard to decouple colour entirely from its associations with life and universal reality.

A sequence of eight paintings by German artist Katharina Fritsch, for instance, in which panels of densely saturated colour appear in gilded old master frames, may well connect back to the colour grids of Fritsch's compatriot Gerhard Richter. They may also, as the curators reveal, call upon childhood memories (the artist's father was a salesman for Faber-Castell, makers of those richly coloured pencils).

But the magic of Eight Paintings in Eight Colours does not lie in the tension between extravagant lushness and empty gloss, nor in any abstract property. It is that each painting, blank as it is, summons something figurative just by dint of pure hue - the golden icon, the blue portrait, the wintry-white landscape; a whole museum conjured with rectangles of framed colour.

Colour Chart has one other remit, which is to explore the idea of colour as readymade, the found material of a painting. This is Frank Stella using household paint in the 50s because it was cheap, and he famously wanted each painting "to look as good as it did in the can". Or Robert Rauschenberg sticking with a paint colour until it ran out; or Dan Flavin restricting himself to the light bulb colours he could get in the hardware shop.

But any show that selects according to method more than effect has it chronic restrictions. The trick is to enjoy the ideas - how colour may be deployed, detached, liberated, conceptualised - while rising above them; and a lesson to that end is there from the start. Ellsworth Kelly's Spectrum Colors may be arranged by chance, true and intellectually striking, but fluttering among them are the squares that let the painting breathe and lift into motion and light. These are what distinguish Kelly from Richter and, indeed, every other artist: little portraits of that other character, the mysterious colour white.