Based on your description it does not sound like you have a defense, but it does sound like you may have mitigating factors that the judge could take in consideration when sentencing you. For civil infractions, there does not necessarily have to be an intent to break the law. For example, if you're doing 65 in a 55 but you didn't realize it until the cop turns on his sirens behind you, it still means you were doing 65 in a 55. Same thing with the no right turn. It may have been hard to see the light and you did stop before it changed but it doesn't necessarily mean you're not in violation. You have three options, go to court and explain to the judge, take the class, or hire an attorney who might be able to get you a better result.
I might be missing something, here, but you probably should not have stopped on the yellow. You are permitted to enter an intersection on a yellow light, particularly if you cannot safely stop behind the limit line prior to light turning red, and you would have been fine if you had completed your turn on the yellow light. You stopped, however, at the yellow warning light, which was your option. You should not thereafter have gone once the light turned red. The Judge may see an exception for you if you had entered the lane legally on the yellow, but were then prevented from continuing by other cars turning in violation of their signal (as no opposing signal could be green while yours was yellow). If, however, cars were turning left on their green light, and you, from behind the limit line, after stopping for a yellow, then turned against your red signal on a 'no right on red' intersection, it's pretty tough to see how you are not liable. You could argue that you could not see the sign, but then, given that cars were entering your lane from their left turn (ostensibly, with their signal), and that you had stopped, you would also have had to be unaware that the intersection was 'no right on red'.
The facts you outline in your post suggest that you will have little likelihood of proving a successful defense. Concerns like dim lighting on a bright day merely outline conditions present for which you have the responsibilty of dealing with as a licensed driver.
That there was no intent to break the law also provides no grounds for you to prevail.
You will have an uphill battle should you decide not to pay the fine and challenge the ticket.
Good luck to you.
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