History channel President Nancy Dubuc knows what she's up against running a cable television network devoted to events from long ago in an age of real-time tweets and quirky videos that go viral instantaneously. History, people automatically say, is black and white and fuddy-duddy," she said matter-of-factly. But not according to Dubuc. Since taking over History three years ago, the young executive has sought to recast the network in Technicolor. To do so, she's undertaken a provocative strategy: severing the cable channel's tether to the past.