… is a neologism based on "whitewashing," to superficially cover over a problem to approve appearances--without solving the problem. "Whitewashing" is a metaphor based on coating a house or a fence, as in the beginning of the novel Tom Sawyer, with whitewash (which is not paint, but a mixture including water and lime or chalk).
Greenwashing (apparently coined in the 1980s)1 is a company's attempt to cover for poor environmental practices with minor changes to its business or with a marketing campaign. My favorite example is the BP logo:
A green sun for a company that primarily deals in oil, and has spewed many millions of barrels of it into the Gulf of Mexico. BP says that the logo "symbolises a number of things--from the living, organic form of a sunflower to the greatest source of energy...the sun itself." But it's clearly an attempt to capitalize on customers' interest in environmentally-friendliness, just by changing a picture.
My favorite example of a company that appears NOT TO engage in greenwashing is the Sherwin Williams paint concern:
1. My cursory search for the earliest use of "greenwashing" led to a Time article from 1985, where it means "money laundering."