Blackmon, whose three hits in the series were all homers, tied the game with a leadoff drive against Zack Greinke in the sixth inning. He added another leadoff shot against Fernando Salas (0-1) in the eighth.
After scoring 17 runs in the first two games, Arizona managed only an unearned run in the series finale.
Bryan Shaw (1-0) pitched a scoreless seventh to get the victory. Jake McGee retired the heart of Arizona's lineup in order in the eighth, and Wade Davis pitched a perfect ninth for the save in his Rockies debut.
Greinke and Rockies starter German Marquez each had a solid performance.
Greinke, a 17-game winner last season who had his first start pushed back by a minor groin issue in spring training, struck out nine in 5 2/3 innings. Marquez allowed four hits, struck out four and walked four in five innings.
The Diamondbacks took the lead in the fourth.
Daniel Descalso singled with one out and Jarrod Dyson hit a bouncer toward second base. Shortstop Trevor Story booted the grounder into center field and Descalso advanced to third. He scored when Nick Ahmed grounded into a fielder's choice, barely beating out the potential double play.
Greinke blanked the Rockies for five innings on three hits before Blackmon caught the pitcher's slow curve ball on the first pitch of the sixth and sent it into the right-field seat. Greinke fanned Nolan Arenado and gave up a single to Carlos Gonzalez before manager Torey Lovullo made the pitching change.
Diamondbacks: RHP Randall Delgado (on the 10-day DL with a left oblique strain) threw 30 pitches in a bullpen session on Friday. RHP Shelby Miller, on the 60-day DL recovering from Tommy John surgery, threw 35 pitches in his session.
The Diamondbacks commemorated their 20 years in the majors with the starting pitcher of their first game, Andy Benes, throwing out a ceremonial first pitch to Jorge Fabregas, his catcher that day. Sam Moore of Sam and Dave's ''Soul Man'' fame sang the national anthem, just as he did in that first game in 1998. The first 20,000 fans got jerseys in the team's old purple pinstripes with the No. 98, the year the team began play.
Both teams have Sunday off.
The Rockies send right-hander Chad Bettis to the mound Monday night in the opener of a three-game series in San Diego.
Arizona opens a three-game series at home against the Los Angeles Dodgers on Monday night, with right-hander Taijuan Walker on the mound for the Diamondbacks and right-hander Hyun-Jin Ryu going for the Dodgers.
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