This allows you to add your own creativity to the robot's appearance. If you wish, simply sand the surface a little to create a nice looking texture. You can also use common spray paint of any color. We recommend using a primer designed to adhere to metal. We also recommend a little sanding and cleaning before painting - see the instructions on the back of the spray can.
Most hardware stores carry good spray paint and primer for a few dollars per can.
One can of each will be more than enough. Primer usually dries in less than 15 minutes but you normally need to let the top coat of paint dry overnight. Be creative, consider adding colored tape and other flashy ideas to make your robot stand out. It may be necessary to clean out holes on the robot that have a build-up of paint. Simply use a pocket knife or exacto knife to clean them out.