WHO, WHAT, WHY?
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Conservative leader David Cameron is urging people to "vote blue, go green." Labour has branded Cameron a "chameleon... available in any colour (as long as it's blue)". But why are the Tories blue, and for that matter why is Labour red?
Cameron puts environment at centre of Conservative campaign
Politicians often complain that instead of talking about their ideas and policies, people take more notice of the colour of the tie they're wearing.
But colours are important to political parties - they're part of the identity, appearing on posters, rosettes and conference backdrops.
And subtle shifts in colour, such as Tony Blair's imperial purple ties, are interpreted as reflections of political intentions.
Red has been the colour most strongly associated with the Labour Party since its foundation in 1900.
Historically, radical republicans and socialists first adopted a red flag in the 1848 French revolution - which reinvigorated the ideals of the first uprising, in 1789 - to represent "the blood of angry workers" and it is still widely seen as the colour of the political left.
But as Labour softened in the 1990s, so, briefly, did its colour scheme. The party used purple rather than red as a background colour in its 1997 election broadcasts as it targeted central ground and Gordon Brown said "purple is the colour of passion".
It is seen as an expensive, smart colour and currently fashionable, says Jenny Cutler, an image consultant.
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Historically, the Conservative Party's colours were those of the union jack: red, white and blue. But when Labour staked its claim to red, the Tories edged towards blue alone as its party hue.
Blue is a colour associated with smart presentation, says Ms Cutler.
Conservative parties throughout the world have adopted blue as their colour although the US is a notable exception, with the Democratic Party, which tends to represent labour rights, represented by blue and the Republicans, which has stronger allegiance to big business, employing red.
'Vote blue, go green'
As the Conservative Party also seeks to shift towards the middle ground, the colours on the party's website are now looking increasingly pale blue, with a light sprinkling of green.
Blair at Labour Party conference
And with the Conservatives adopting the slogan "Vote blue go green", party leader David Cameron has been seen sporting a green tie.
The other green party, the Green Party, formed in 1973, has a name that combines a colour and a cause, with its identity drawn from the environmental movement. Green Party spokesman Keith Taylor says Cameron's attempts at becoming environmentally friendly will "convince no-one".
The Liberal Democrats, meanwhile, have wavered between orange and gold - recalling the yellow that was the colour of the Liberal Party from which the Lib Dems emerged.
Add your comments on this story, using the form below.
Party colours dont matter, what matters is integrity and whether you actually beleive what the parties involved are saying. To use colour as a basis of which party to vote on is to underestimate the knowledge of the public.
Steve Toone, Sheffield
Given that politics, and politicians, are generally dull nowadays, it's amazing nobody has adopted grey.
Graeme, Dundee, Scotland
It's interesting that it's the reverse in the US - the Dems are blue and the Republicans red.
Matt Reynolds, Denver/US
I was led to believe that the nineteenth century Tories, long before Labour came on the scene, adopted blue after the fighting colours of a particularly popular boxer/pugilist.
Jock Coats, Oxford, United Kingdom
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