Untrue colours

You can't trust colours. They are shifty and they are promiscuous. They don't just sit there on the picture plane. Some colours advance, generally the hotter ones, while cooler hues recede

Next time you see a painting on a poster or a postcard, in the pages of an art book, online or in a catalogue, don't entirely believe it. When it comes to painted canvases, all reproductions lie.

Even smart people forget this. When Microsoft's Bill Gates built his billionaire's mansion on a lake near Seattle, he didn't bother buying paintings.

Instead he'd program screens set into the woodwork. "You'll be able to call up,'' he wrote, "portraits of presidents, pictures of sunsets ... or reproductions of High Renaissance paintings.''

Already he'd arranged access to great art. Through his Corbis company, Gate had bought the right to digitise the pictures in fabulous museums, the Hermitage in St Petersburg, Russia, the Barnes Foundation in Philadelphia.

His options were immense. He could tap on a few buttons and the Hermitage's Leonardo da Vinci, the great Benois Madonna, would show up in the room. Of course it didn't work. Gates's Leonardo wouldn't look like a Leonardo. It would look like a Leonardo on TV.

All wrong
Screens will never cut it. They're the wrong shape (the Leonardo has a rounded top), and the wrong scale. And video displays never get the colours right.

Technology can't solve this. Pixels aren't paint; canvases are not packets of digitised information - they're complicated objects getting older every day. There's a moral to this story. Colours: You can't trust them.

To test this proposition: When next in a museum, first buy yourself a postcard, then go and find the painting it pretends to reproduce, and compare them side by side. You'll see. The card will be demolished by the real thing. Colours are like that. They're shifty and confounding and they will not stay in place.

Infected by neighbours
Colours are promiscuous. They get infected by their neighbours. Anyone can test this. A colour chip of brilliant red, when held up against other hues, will suddenly go orange, or purply, or pink.

The tricky, preternatural shiftiness of colours was useful to artist Gene Davis. When reproduced in textbooks, or shown in constant light in windowless museums, his stripe paintings look paralysed.

But his pictures breathe in changing daylight. They're not the same in summer as they are in winter. They're different in the red of dusk than they are at noon.

Scientists, though not poets, will tell you that the hue you see is essentially a matter of the wavelength of the light. They can assign that mauve a number.

What that number does not tell you is that colours seem to move, they don't just sit there on the picture plane. Some colours advance, generally the hotter ones, while cooler hues recede.

Davis understood this. There's no perspective in his 10-foot-wide Narcissus. What pries open its space is the way its stripes decide either to retreat or step into the room.