You have a chance at winning but remember that without a witness it's simply what you saw vs. what he saw. If you have a large piece of posterboard then diagrams of the intersection and where your car was at when the light turned yellow help illustrate the situation.

My guess is that if it's simply you vs. him you'll just get a reduced fine. The judge doesn't want to blow off the cop and **** off the force by not backing them up but at the same time he can't treat you unfairly. If it comes down to your word vs. his the judge is most likely going to meet you both in the middle. If the opportunity arises you could request a 6 month deffered judgment. This typically means that in the event you don't get any tickets in the next 6 months the charges are dropped. If you get a ticket then they both stick. That's one way to allow the cop to save face, the judge has an easy decision and if you keep your nose clean you've got nothing to worry about. just a thought.