Can you legally paint a keg and take it in to a store to get it filled with something like an energy drink?

My friend has this crazy idea about going to get an empty keg, paint it up and then take it to a store to get it filled up with an energy drink. If this could be done (taking the empy keg to a store and them filling it up) would it be smarter to paint it BEFORE we take it in or AFTERWARDS? Crazy ideas run in my life and this is the newest one. Any insights helpful :D