Answer based on context:

Following their third loss of the season, the Indianapolis Colts entered their home game against the Cincinnati Bengals with a chance to regain the lead in the AFC South.  Indianapolis came out energized in the first quarter where the Colts picked up a field goal with three minutes remaining in the quarter, and a Kelvin Hayden interception returned for a touchdown.  The second quarter continued to see Colts dominance with a Javarris James touchdown run, extending the Colts lead to 17-0.  However, as the quarter wore on the defense began to allow larger gains and the Bengals were able to score a touchdown and a field goal in the last ten minutes of the half.  However, an Adam Vinatieri field goal gave the Colts a 20-10 lead going into halftime.  The Colts came out in the third quarter sluggish and both teams exchanged the ball throughout the rest of the quarter.  Another Vinatieri field goal gave the Colts a 23-10 lead.  With everything seeming secure, the Bengals were able to pick up a touchdown on a 19-yard pass from Carson Palmer making it a six-point game.  The Bengals onside kick attempt was successful with a late penalty by the Colts, giving the Bengals the ball at the Colts 40-yard line.  A fumble, the fifth turnover by the Bengals on the day, gave the Colts the ability to hold on to the lead and win the game 23-17, going to 6-3 on the season and taking first place in the AFC South by one game.

How many points did the Colts lead by at halftime?
10