Can tri iodine turn gray hair darker?

Supporting the thyroid, which iodine does, may make a difference in the body's metabolism, immune system, and possibly even hair growth. While it could result in your hair growing in thicker, faster, and more healthy overall, it probably wouldn't affect the color of your hair. Hair color changes over time - (for instance, light blonds become medium blonds, and just about everyone goes gray), but iodine probably wouldn't affect hair color directly.