Why do referees have those black bands on the hands?

In 2006, the NFL completely redesigned the shirts, going to a sleeker-looking uniform which, however, no longer identified a given official's position from the front. Also new for 2006 were black pants with a white stripe down the side to be worn in cold weather. These looser-fitting pants allow for layering of warmer clothes underneath. Beginning with the 2010 season, college officials and, in many states, high school officials, have the option of wearing the black cold-weather pants.