It is a warning light to make sure you know that the light is changing or there is a school ahead or a school bus is stopped warning you children are getting out or getting in also an intersection is ahead!
Obviously it means the light is gonna turn red soon. You have two options...based on where you are. There is a point of no return (Smith System Advanced Driver Training) where it is not possible for you to safely stop...so you proceed thru the light before it turns red. If you are not to that point...you come to a stop as or just after the light turns red...maybe even a second before. Rule of thumb...SAFETY FIRST!