Spread a drop cloth across a wide, flat surface outdoors.
Dampen a sponge and wipe down each of the trays you removed from the refrigerator. Dry them off with a clean, dry cloth. Do not attempt to paint the shelves unless they are completely dry.
Take the cap off a can of aerosol metal primer and shake the paint for about 2 minutes. Spray the metal primer on the front of the shelves, moving in sweeping motions about 2 inches from the surface of the shelves. Allow the primer to dry completely -- about 24 hours -- before turning the shelves over and spraying the back of them.
Take the cap off a can of aerosol metal top coat in a galvanized metal finish. Spray the front and back of the shelves with the top coat and allow the paint to dry completely before putting them back into the refrigerator.