Coming off a two-game winning streak, the Broncos headed to Lucas Oil Stadium to play the undefeated Colts. In the first half, the Colts jumped out to a 21-0 lead. Denver finally scored when Kyle Orton found Brandon Marshall in the end zone going to the locker rooms trailing 21-7. For most of the second half, the Colts offense sputtered. In a long drive, Orton found Marshall for his second touchdown, however, the two-point conversion was no good, making the score 21-16. Then the Colts offense got things going late in the fourth. After a long drive, Manning found Dallas Clark in the end zone for his third touchdown of the day, putting the Colts on top 28-16 with under three minutes left in the game. On a long fourth down, Orton found Marshall who lateraled the ball to a lineman who was tackled short of the first down. With the win, the Colts broke an NFL record with 23 straight wins. Though despite the loss, Broncos WR Brandon Marshall had a record of his own with 21 catches beating Terrell Owens' record.

Based on the above article, answer a question. how many points did the colts lead in the first?
21