NEW YORK, April 19 A growing number of men in the United States are dropping their white underpants in favor of more exotic and wacky ones.New specialty shops and Web sites marketing such designs as pink underwear with white piping, fire trucks, hot dogs and even Batman and other superheroes report booming sales, the New York Times reports.As evidence, in 2006, sales of plain white briefs dipped below 50 percent for the first time in decades, if not ever. Yet, the NPD Group, which monitors clothing trends said from 2004 to 2006, sales of men's knit underwear rose 5.3 percent, to 397 million pairs.In Portland, Ore., entrepreneur Steven Lien opened a men's underwear store called Under U 4 Men five months ago, and he told the Times he's not looking back."The store was profitable within 30 days," he said. "And I didn't open on Gay Street, U.S.A. I opened on Main Street, U.S.A." Copyright 2007 by UPI