Refinishing your cabinets may mean that the color of the existing hinges no longer matches, and while you can always replace the hinges, it's less expensive to paint them. There is another, more important advantage: The hinges fit the existing holes, so you won't have to drill new holes or fill the old holes. Use spray enamel for the hinges because, if you prepare the hinges properly, it's less likely to chip and peel when you open and close the doors than paint.
Unscrew the hinges from the cabinet doors and remove the doors; then unscrew the hinges from the cabinets themselves using a screwdriver. Put all the screws in a safe place -- you'll probably want to paint them as well as the hinges.
Wipe the hinges down with denatured alcohol to remove any grease or grime. Concentrate on the parts that are visible when the hinges are installed.
Sand the visible parts of the hinges with 220-grit sandpaper to scuff up the existing finish or -- if the hinges are unfinished -- the bare metal. This ensures better paint adhesion.
Set the hinges flat on a a sheet of old newspaper with the parts you want to paint facing up. If you plan to paint both sides, the most visible sides should be face-up.
Put on a respirator and spray a coat of metal primer on all the hinges, using an aerosol can. Let the primer dry for 30 minutes to an hour; then turn the hinges over -- if you're painting both sides -- and spray the other side.
Spray the hinges again with metal enamel. If you're painting both sides, spray the undersides first; wait an hour for the paint to dry; then spray the top sides. Line up all the screws on the newspaper and spray the heads to make them the same color.
Wait one to two hours for the paint to dry; then spray a single coat of clear lacquer. The lacquer adds extra gloss, and it protects the paint from chipping. Let the lacquer cure overnight before installing the hinges on the cabinet.