Remove the dryer vent from the wall using a screwdriver to loosen the bolts.
Sand the entire surface of the dryer vent with 240-grit sandpaper.
Dip a clean rag into warm, soapy water and squeeze it out until it's no longer dripping. Clean the sanded dryer vent, rinsing the rag in the water as necessary. Rinse thoroughly.
Buff the dryer vent dry with a soft cloth.
Place the dryer vent face-up on top of a large piece of old drop cloth.
Shake a can of metal spray paint in the same color as the wall surrounding the dryer vent. Hold the nozzle about a foot away from the vent and spray a thin, even layer over the front of the dryer vent. Allow it to dry.
Apply a layer of sealant over the newly painted dryer vent. Allow it to dry.
Replace the dryer vent on the wall using the screwdriver.