This week we changed to a new Charter Cisco Explorer 4640 box. The medium gray bars were distracting, but we don't like the stretch or zoom options. The dark gray is like soft black, which is exactly what we were hoping we could change to. It blends much better with the television's frame.
As you explained, the tech support people for Charter do not seem aware of this setting, or how to navigate to change it. I have been searching the Cisco site for this information, and decided to search Dogpile for a forum guru who had shared this information. And here you are. Thank you for sharing this We're all smiles here thanks to you!