Google Contributor is terrible. Not because it doesn't work, but because it still leaves big green gaps where the ads were saying, "Thank you for using contributor!"
Not even mentioning the fact that it only works on a minority of ads, the green boxes are even more annoying than the ads were.
You can configure it to render transparent images, so you see the site's background. Hit the 'gear' in the upper right of the Contributor site, and the options are neutral-grey, transparent, cats, and 'soft focus'.
Not even mentioning the fact that it only works on a minority of ads, the green boxes are even more annoying than the ads were.