Green number plates, green cars, green as grass?
"Green number plates have the potential to be a powerful motivator to encourage road users to shift to cleaner vehicles"
As in "encourage the rich to buy expensive new cars that shift the pollution from the road to the power station".
Practically every single "green initiative" so far has (probably unintentionally) merely made it possible for the rich to carry on as before while limiting the options of the poor.