Thank you for your question. I look forward to working with you to provide you the information you are seeking.
If the turn looked 90 degrees and you show up in court with pictures of the intersection showing no sign indicating no right on red, you have a good chance of getting the judge to throw the ticket out. The issue will be a visual issue of fact for the judge to determine based on the photograph you present of the intersection showing that the turn was a real right turn and as such it would be a permissible turn.
When you say it was a "straightaway, but it looked like a 90 degree turn," I cannot actually picture what you are talking about so perhaps if you could include a picture we could help you better, but without a picture, what we can tell you is that if this did require you to make a right turn, 90 degrees, then you have a good case of showing the judge that it indeed was a right turn even if it was on the same road and without a sign prohibiting such a turn it would lead a reasonable driver to believe the turn was permissible because it was indeed a turn.
I truly aim to please you as a customer, but please keep in mind that I do not know what you already know or don't know, or with what you need help, unless you tell me. Please consider that I am answering the question or question that is posed in your posting based upon my reading of your post and sometimes misunderstandings can occur. If I did not answer the question you thought you were asking, please respond with the specific question you wanted answered.
Kindly remember the ONLY WAY experts receive any credit at all for spending time with customers is if you click on OK, GOOD or EXCELLENT SERVICE even though you have made a deposit or are a subscription customer. YOU MUST COMPLETE THE RATING FOR THE EXPERT TO RECEIVE ANY CREDIT, if not the site keeps your money on deposit.
Also remember, sometimes the law does not support what we want it to support, but that is not the fault of the person answering the question, so please be courteous.