Colvin connected for two-run homers in the fifth and eighth innings in Colorado's fifth win in the last seven starts.
Carlos Gonzalez added a three-run shot for the Rockies and Jhoulys Chacin (4-3) held on for his first win since April 19 with two runs on seven hits over five innings.
Span's two-run double in the second inning gave Washington a 2-0 lead; however Colorado came to life in the fifth by batting around and putting five runs on the board.
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