Paint is a conductor, therefore painting
an outlet can cause a fire, very easily just based
off of a spark!
You can buy conductive paint, but wall paints used in homes these days typically aren’t conductive. However, painting over receptacles isn’t a good idea because you’re introducing foreign materials into the socket of the plug which could easily interfere with the continuity between the pigtail of the appliance you’re plugging in and the receptacle. Less contact area to pass the current = more heat, and more heat could lead to fire.
As stated previously. Painting over outlets allows the possibility of a conductive matter to enter the outlet that may cause a short or a shock to the painter.