Vote blue, go green. That was the slogan David Cameron adopted when he took control of the Conservative party..
The company's marketing and legal brains got a hint that the EU was looking at a law that would severely restrict the use of the world 'green' to describe any new product. Indeed, it might be argued that anything 'manufactured' cannot be, by definition, green.
The way round the problem, the car maker decided, was to follow Mercedes' lead and adopt the word 'blue' to mean 'green'. And this quiet trend has been gathering force.
Merc's super-clean Bluetec diesel engines came first, followed by the fuel-sipping Volkswagen Blue Motion range. Then Hyundai's low-Co2 iBlue series appeared. And the facelifted BMW 3-series range will include a 330d fitted with the new super-low emission BluePerformance diesel engine.