As far as I know, none of the DC tenant’s rights relate to paint. Paint generally doesn’t affect the habitability of the apartment (unless it’s lead).
Your best bet here is to kill them with kindness. I doubt they will pay to have someone paint it, knowing that they would just need to repaint it after you moved out to cover up any subsequent damage before re-renting. I think it’s fairly likely you would be able to get them to pay for the paint, however, if you ask nicely.