White balls discoloured by the grass are difficult for fielders and batsmen to see in certain light conditions.

BBC: Pink ball makes debut at Lord's

The gym walls and ceiling were a patchwork of pictures, photos and discoloured clippings from newspapers and old boxing programmes.

BBC: South East Wales - Boxing Beats: Fighting Pretty

All that reminds us of the cosmonaut in Klushino is the sagging road sign with peeling, discoloured paint, and an old one-storey house.

BBC: Yuri Gagarin's Klushino: Forgotten home of space legend

They were a Union Flag towel, a green towel with a "Renaissance" label and a fleece which was originally blue and white, but is now badly stained and discoloured.

BBC: Stream baby death: Officers appeal on Crimewatch

It found that 26% of the sample had Tinea pedis, better known as athlete's foot, while 30% had Onchomycosis, an infection that causes toenails to become thickened, discoloured and distorted.

ECONOMIST: Fancy footwork

Because a white ball becomes discoloured towards the end of a 50-over one-day innings, making it difficult for the batsman to pick out, current International Cricket Council regulations state that after 34 overs, the ball must be changed for one of similar age, that has been cleaned and rewhitened.

BBC: Does the white ball behave differently?