Green racked up 158 yards on the ground and scored twice on 20 carries while Colter added 106 rushing yards and a score on 15 tries for the Wildcats (3-0).
Colter also threw for a score, going 6-of-7 through the air for 40 yards.
Tyler Van Tubbergen managed a pair of scoring strikes on 16-of-41 passing for 202 yards with an interception to pace the Broncos (0-3).
Western Michigan's Corey Davis piled up 112 receiving yards and a TD on five catches.
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