The Rockies also belted five homers on a hot and humid day at the hitter-friendly Great American Park in Cincinnati.
Phillips' blast in the third inning gave the Reds a 5-1 lead, while Joey Votto, Jay Bruce and Todd Frazier added solo shots as National League Central-leading Cincinnati took the rubber match of their three-game series and won for the eighth time in nine games overall.
Mat Latos (4-2) earned the victory despite yielding five runs on five hits. The right-hander didn't issue a walk, however, and struck out three.
Aroldis Chapman logged his third save after recording the final five outs.
Rockies starter Jamie Moyer (2-5) was lit up for seven runs on seven hits over five frames. The 49-year-old left-hander issued one walk and fanned a pair.