Officials who want lots of integration can only achieve it, in many cases, with a strong hand and a blatantly colour-conscious mind.

ECONOMIST: The Supreme Court looks again at race in schools

Although he cannot definitely rule out a direct effect by the pollution on the birds' metabolism of the yellow pigment, or its incorporation into their feathers, the correlation between a shortage of caterpillars and faded plumage is strong evidence of a link between pollution, diet and bird colour.

ECONOMIST: Great tits

Upriver here and at the Sandrift River, which runs parallel 10 miles to the east, the colour of the water is striking - imagine looking into a cup of strong, dark coffee.

BBC: The perfect trip: South Africa

It does everything from breeding new seeds and cattle, to creating ultra-thin edible wrapping paper for foodstuffs that changes colour when the food goes off, to running a nanotechnology laboratory creating biodegradable ultra-strong fabrics and wound dressings.

ECONOMIST: Brazilian agriculture