Here's one expert with an answer:
Most (green) marketing ... is ponderous, lacking in humility, humanity and humor...Guilt doesn't sell, but humor does. We need to sell green by poking fun at our silliest excesses, the stereotypes and ourselves.Green marketing should make people feel good. That's not exactly a strong point of the environmental movement. Usually we're busy making people feel bad for all the wrong things they do.
Take a look at the two ads, which do you like? Probably not the green one. Tweet