Luck went 19-of-32 through the air for 180 yards with an interception and Richardson added a score for the AFC South-champion Colts (9-5), who got back on the winning track following a loss to Cincinnati last week.
Case Keenum could manage 168 passing yards on 18-of-34 efficiency with two interceptions for the Texans (2-12), who dropped a franchise-record 12th straight.
They were playing under interim Coach Wade Phillips after this week's firing of Gaby Kubiak, who had guided Houston to two division titles over eight years at the helm.
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