There's been a lot of White WRs used as kick returners, in fact a number who were/are used as kick returners but rarely as receivers. Marc Mariani and Alex Erickson come readily to mind but there's been a bunch over the years. In fact, one season about seven or eight years ago, something like 13 different NFL teams were using a White player as either a punt and/or kickoff returner.
Running back is a different story because there have been so few White RBs, even as backups, and they've tended to be of fullback size, ala Peyton Hillis. McCaffrey, Woodhead and Burkhead have been the three smaller sized ones. Woodhead was used at times to return kickoffs, and Burkhead's returned a few punts. I wouldn't want to see McCaffrey returning kicks, period. I'll always remember the Giants using Jason Sehorn as a kickoff returner one preseason when he was at his peak; he promptly had one of his knees wrecked during one of his first returns and was never the same player afterward.
