It's just called "door molding." These links from GM Parts Direct say "primed" which means it needs to be painted. Don't know if a dealer can get them pre-painted. The diagram is not clear as to whether the first item is just the chrome component.
www.gmpartsdirect.com
www.gmpartsdirect.com
Tom
2009-2017 GM Primed Rear Driver Side Door Center Molding 22763943 | GMPartsDirect.com
2009-2017 GM part # 22763943 - Primed Rear Driver Side Door Center Molding

2013-2017 GMC Primed Rear Driver Side Door Lower Molding 19259498 | GMPartsDirect.com
2013-2017 GMC part # 19259498 - Primed Rear Driver Side Door Lower Molding

Tom