You are fine.
For a ticket (red light) to stick, they have two photos. One showing your vehicle crossing the crosswalk/entering the intersection and one photo of you fully in the intersection. These two are critical as it proves you both entered when it was red and also fully entered. This prevents false tickets based on entering when it wasn't red (ie yellow) at the time you pass the sensors at the crosswalk and also prevents tickets from false triggers when it thinks you entered the intersection but actually didn't.
You are good. If, and this is a big if, you get a ticket in the mail, it will show you entering the intersection on a green anyways (since you say it changed to yellow while you were in it). In this case, the sensors shouldn't even trip the photo (they are activated when the red phase is active).
Now, all that is moot if this is a speed on green intersection as well. It's quite possible you were going faster than you think. Or someone behind you tried beating the yellow and gunned it, which got them a nice speeding ticket. In that case, you won't be the target in the photo. All photos are reviewed before sending and if there's any doubt, they throw it out (usually, the odd one still squeeks through).
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