Why does Home Depot still sell green drywall if it has been banned by code since 2006?

I just saw a renovation program on HGTV or the DIY channel, and they mentioned that you’re supposed to use purple drywall in the bathroom for moisture/mold resistance rather than green board that they used in the past. They even said that green board has been banned from code in 2006. I just went to Home Depot, and they still carry green drywall and they don’t even carry purple, the kind you’re supposed to use anyway.