To paint a washer and dryer black, move them away from the wall, wash and dry them, protect adjacent surfaces, sand the machines, apply primer, and apply spray appliance enamel paint. The supplies you need include masking tape, soap, water, a sponge, a towel, primer and appliance enamel paint.
Unplug the washer and dryer, and move them away from the wall. Wash them with hot, soapy water, and then dry them with a towel. Spread drop cloths or newspapers over the floor, and use masking tape to protect other nearby surfaces.
Search the washer and dryer for flaking paint, rust and exposed metal. Sand those areas until they feel smooth, and then apply a coat of spray primer. Let the primer dry according to the instructions on the can, and then apply one coat of spray appliance enamel paint. Use broad, horizontal strokes, and keep the can in constant motion. This promotes even application. Dry the paint according to the manufacturer's recommendations. Inspect the appliances, and apply a second paint coat if desired.
Touch the machines to verify that the paint is dry. Return the washer and dryer to their proper location, and plug them in. Discard the newspapers and masking tape.