What exactly is in a vitamin C indicator solution?

I am doing a science fair type of project on vitamin C levels in different types of orange juice and I am confused. What do I need to use to determine which has more vitamin C? I have been researching and finding iodine starch solutions but some experiments use just iodine. So what should I use to make an indicator solution and can I do it at home or do I need to use my school's lab for this project?