Green Xanax is the version of Xanax medication that is imprinted with S 90 3 on green rectangular bars. Green Xanax S 90 3 online when a person needs relief from anxiety. The doctor usually prescribe this medication to treat people with anxiety, panic disorder. Green Xanax is a powerful benzodiazepine, a medication highly effective in reducing anxiety. It works by strongly binding to the brain receptor GABA-A, a CNS depressant, and decreasing brain activity.