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In the fight against graffiti, the color white lures, while transformer green repels — which makes the latter very popular with San Francisco’s Department of Public Works.

It’s also practical, cost-effective, and psychologists say it’s a plus because of its association with nature and serenity.

Transformed truck: Before and after the Clean & Green Trucks Program. Photo courtesy Department of Public Works

All of this has enticed DPW’s and the General Services Agency’s central shops to bet some $15,000 that the paint will deter future tagging on trucks and lessen the urge to tag, which costs the city $20 million a year in abatement. That means almost 30,000 requests a year, or more than a 100 a day, according to Greg Crump, a member of DPW’s Graffiti Advisory Committee.

Since March, the Clean & Green Trucks pilot program has been offering owners of commercial vehicles covered with graffiti a free professional paint job.

So far, 14 trucks have been painted transformer green, which got its name because it was used to paint transformers.

“I think the issues are primarily pragmatic,” said Professor Stephen Palmer, director of the Visual Perception Laboratory at the University of California, Berkeley’s Psychology Department, about the choice of the dark green color. DPW staff agrees; five years ago the city switched colors from dark gray, and transformer green now covers trash cans and light poles.

Department of Public Works fixture colors.

Besides being dark enough color to cover graffiti, the paint color is cost-effective in other ways as well. It needs no primer, for example, and paint donated by contractors and mixed together comes out transformed this particular green.

Psychologists also say green has positive associations. In their paper “An Ecological Valence Theory of Human Color Preference,” published in the proceedings of the National Academy of Sciences this year, Palmer and Karen Schloss reported on the 48 participants’ responses when asked to rate their preference for 32 chromatic colors.

They liked transformer green, associating it with nature, healthy vegetation and Christmas. “It represents greening the city,” Crump said.

Green is also associated with success and sadness, and is considered a calming color, Palmer said. He doubts, however, that that would deter taggers. “The dark colors that people like most are dark greens, reds and purple. But I wouldn’t paint a truck dark red or dark purple.”

So far the strategy has worked for Public Works. As of September 2010, not one of the newly painted trucks has been tagged.