In this photograph taken Saturday, April 25, 2015, grow lights turn the color of marijuana plants under cultivation to yellow as a contingent of lawmakers, their staffers and a handful of lobbyists toured one of two retail and grow operations for both medical and recreational marijuana in northeast Denver. Colorado's unusual tax law is forcing the state to suspend taxes on recreational marijuana for one day, Sept. 16, during which a 10 percent sales tax and 15 percent excise tax will not be collected. (AP Photo/David Zalubowski)