Yellow Xanax is rectangular with an imprint of R039 and has a strength of 2 mg. It is also known as yellow school bus bars... moreYellow Xanax is rectangular with an imprint of R039 and has a strength of 2 mg. It is also known as yellow school bus bars and has three grooves, making it simple to divide by four. If you want to buy a yellow xanax bar online, make sure they match the pi...