David Cameron, the newish head of the Conservative Party in the UK, has a new slogan for the forthcoming local elections: "Vote blue, Go green". This is a bit more catchy than "Vote blue, Go right." The colour of the UK Labour Party is red, and the colour of the third party, the Liberal Democrats, is orange-yellow. Plotted against the visible colour spectrum (ROYGBiv), from left to right, those colours would nominally seem to fit.1
