DENVER — Jason Vargas threw seven strong innings, Kyle Seager homered and drove in three runs, and the Seattle Mariners beat the free-falling Colorado Rockies 10-3 on Saturday. One day after being victimized by Kevin Millwood’s two-hitter — his first shutout in nine years — the Rockies looked lost against Vargas, who took a two-hitter into the seventh to help hand Colorado its 12th loss in 15 games. Vargas (5-3) kept the Rockies off-balance with an array of offspeed pitches set up by pinpoint control of his fastball. And on a cold and damp day where the vendors’ shouts of “Hot chocolate here!” drowned out the usual “Ice cold beer” screams, Rockies rookie left-hander Christian Friedrich (1-1) fizzled in his first start at Coors Field.