Are you frozen by fear in the paint-chip aisle? Panicked at picking the "right" neutral? Whipsawed by confusion about accent walls? Let's face it: The trickiest part of readying a roller is settling on the right color. The choices seem endless, the rules elusive. But don't throw in the drop cloth quite yet. We queried pros far and wide to home in on useful advice—read on for tricks everyone can use.