Xanax bars come in different colors and strengths, treat anxiety disorders, and lessen panic attack episodes. Xanax belongs to the class of benzodiazepines that mainly help to heal GAD(generalized anxiety disorder) and balance the GABA in the brain. However, some patients find ease in as short as 20 minutes and stay calm for 2 to 11 hours. Although, green xanax bars stay in the body for up to 3 days after initial use.