Bobs Photochromism

[SimonMac]

If they are left in the sun do they change colour?

[bless 'em all]

If they are left in the sun do they change colour?

The one I hit over the head and chucked out the window changed colour after while. The greeny-blue colour suited him.

[KentPhilip]

Tens of thousands of years after immigrating to the UK, the descendents of the bobs will turn white due to the reduced amount of sunlight.
It's not racism, it's evolution. Just as we are descended from the blacks of darkest Africa before we came to northern Europe and went white.