Replace the question mark with a number

A man was in a hurry to meet his friend down at the nearby lake. On the way down there, he was stopped by a man fully dressed in red. The man pulled over, and the red man asked, "Hi, I'm the red jerk of the highway. Have anything to eat?" The man smiled and handed him a sandwich. He continued down the highway and was yet again pulled over by a man fully dressed in green. He stopped and the guy in green said, "Hi, I'm the green jerk of the highway. Have anything to drink?" Without smiling, the man handed the green guy his coke. He started off again and started to speed down the highway. Yet again he was stopped by a guy fully dressed in blue. Sighing, he pulled over and pulled down his window, leant out and said, "Let me guess. You're the blue jerk of the highway. What do you want?" "Registration and license please" came the reply.