Is 'Blue' the new 'Green'?

It’s a known fact that fossil fuels, from which gasoline and diesel that powers almost all the automobiles on earth are made, are not going to be available for eternity. From hugely successful and mass-produced gas-electric hybrids to relatively lesser successful full electrics to the still-under development fuel cell and hydrogen vehicles, automobile companies are draining the brains of their experts to find an alternative to replace the traditional Internal Combustion Engines.

While its going to take at-least a decade or two for this seemingly never-ending quest to come to an end, car companies cant afford to sit still until then. They have chosen to make the existing IC Engines cleaner and more fuel efficient. When so much efforts are being put, would any company want them to go unnoticed? The answer is an obvious no and here starts the problem of branding them, typically with a catchy surname pointing out their 'doing good to nature' quality.

Universally, everything that is 'environment friendly' are coined with an adjective ‘green’, which is quite understandable as green has always been tied to nature. But what is most surprising is how a host of manufacturers have chosen to ignore this and call the greener variants of their models ‘blue’. While Mercedes-Benz has chosen ‘Blue Efficiency’ to denote their models specifically tuned for better fuel efficiency and lesser emissions, Volkswagen prefers to call them ‘Bluemotion’ and Hyundai has come up with a ‘Blue Drive’ moniker for the same.

Is there any out-of-the-world relationship between blue and green or is 'blue' really the new 'green'? I don't quite understand.