Here's one of the USA's 16 Go Green Forever stamps issued in 14 April 2011. The sheet was designed by award-winning illustrator Eli Noyes, in collaboration with art director Derry Noyes. The designs on the sheet illustrated simple things we can do everyday to save the environment. An example shown here is the carpooling.
Sharing this green car for Viridian's 142nd roll of Sunday Stamps, for the theme 'cars'.
Source: USPS.com - Go Green