Still trying to get their first win of the season, the Rams went home for a Week 7 interconference duel with the Indianapolis Colts.  St. Louis would trail early in the first quarter as Colts quarterback Peyton Manning completed a 6-yard touchdown pass to wide receiver Reggie Wayne.  The Rams would answer with a 30-yard field goal from kicker Josh Brown, but Indianapolis answered with Manning's 27-yard touchdown pass to tight end Dallas Clark.  Afterwards, the Colts would get the only score of the second quarter with running back Joseph Addai's 6-yard touchdown run. St. Louis would begin the third quarter with Brown booting a 45-yard field goal, yet Indianapolis continued their domination as cornerback Jacob Lacey return an interception 35 yards for a touchdown.  In the fourth quarter, the Colts closed out the game with Manning's 8-yard touchdown pass to wide receiver Austin Collie and running back Chad Simpson's 35-yard touchdown run.
Question: How many different running backs for the Colts scored a touchdown?
Answer: 2