Once every possible length had been tried, the only way to impress the world was through colour: rainbow-hued Mohawks, stripes and wings.

ECONOMIST: Hair, beards and power

The former wife of the president, Winnie Madikizela-Mandela, told mourners that if South Africa was a rainbow nation, the rainbow did not appear to include the colour black.

BBC: Mandela warns ghosts of apartheid haunting S Africa

So called rainbow proteins (a spin-off from work into bioluminescence), which change colour in response to particular compounds, are also an option for detecting environmental toxins, or the potential agents of terrorism.

BBC: The light fantastic: Harnessing Nature's glow

Red is the colour of love and that will be the colour of the lights radiating from the historic building on St Valentine's Day, while rainbow colours will mark Belfast Pride in July.

BBC: Rays of light over Belfast City Hall