By Andrew Gould The Boston Celtics are about to commence a second-round series with the Milwaukee Bucks on Sunday afternoon. While they’ll look to replicate last round’s stellar sweep over the Brooklyn Nets, Marcus Smart will start this clash with a new look. Boston’s tenacious guard showed up at TD Garden rocking green hair. The Defensive Player of the Year is clearly loyal to the franchise that drafted him with the No. 6 pick eight years ago. Smart played a pivotal role in the opening round, averaging 16.5 points, 7.0 assists, and 1.3 steals through four games. The 28-year-old is often credi…