Nick Clegg, whose party colours are usually a bright shade of yellow, was looking distinctly blue yesterday as he met party activists for a question-and-answer session in Glasgow. Police said that a 20-year-old man had been arrested after blue paint was thrown at the Deputy Prime Minister.
Two men are understood to have entered the closed meeting and one of them threw paint, most of which hit Willie Rennie, leader of the Scottish Liberal Democrats. Mr Rennie said: "It was two disgruntled individuals, who chose not to speak about their concerns in advance but were purely interested in doing a stunt.
"Their behaviour has only obscured any message that they may have had. I've always wanted a blue streak in my hair but my mother wouldn't let me."
Mr Clegg, who was left with traces of paint on his face and clothes, also made light of the incident. He told Scotland's Real Radio: "These things happen. It's not a big deal."
Mr Clegg carried on with his political engagements after the incident. The practice of throwing eggs, paints or other harmless missiles at public figures is popular with a certain kind of protester – though the effect is often to rouse public sympathy for the victim.
Rupert Murdoch had a foam pie shoved in his face while he was giving evidence to the House of Commons Culture and Media Committee earlier this year.
In general, the reaction of those who saw the televised incident was to empathise with the media mogul's wife, Wendi Deng, who delivered a resounding slap to her husband's assailant, Jonnie Marbles.
When Peter Mandelson was Business Secretary, two years ago, he had green custard thrown over him by a protester, Leila Deen, who was from the Plane Stupid group, as he arrived at the launch of a low-carbon summit.
In 2004, a member of the Fathers-4-Justice protest group got into the public gallery in the Commons during Prime Minister's Questions and then threw some purple powder, which hit Tony Blair.