With the Rams trailing 60-58, Pierce Hornung grabbed an offensive rebound and kicked the ball out to Green, who drained the decisive trey.
Green (16 points, six assists) later drove for a game-clinching layup and added a foul shot for Colorado State (20-4, 7-2 MWC), which notched its 27th straight home victory.
Greg Smith added 15 points, seven rebounds and four helpers while Hornung finished with 12, eight and four as the Rams took their fifth straight overall.
Chase Tapley netted 16 points for the Aztecs (18-6, 6-4).
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