Lightening the color of dark red brick is a faux finishing exercise that requires a bit of finesse and artistry. Since there are a several ways to execute the project that are all irreversible, performing a test on brick samples is the best way to start.
Things You'll Need
Pressure wash the brick. Any dirt, moss, or other foreign matter will not permit your coating to adequately adhere. Allow the surface to completely dry.
Pour two gallons of water into a bucket. Add a 1/2 cup of Portland cement and stir well.
Saturate the sponge in the water and squeeze it out. Dab the brick evenly with the face of the sponge at about one square foot of brick per side of the sponge.
Add more cement to the water if it does not lighten enough with the first batch. If it is too light, you can wash it off with water within a few hours of application. If it does not come off with water, you must scrub it off with a 1:10 muriatic acid to water solution. Portland cement will set up and adhere if left too long after application.
Paint the brick if the Portland cement does not create your desired result. Use a smooth roller and apply the paint slowly to avoid painting the mortar joints if you want them to contrast.
Plan to do this work when you have several dry days in a row. The Portland cement mix can wash off if rain hits the brick within 24 hours.
Muriatic acid is corrosive. Follow appropriate safety procedures if you use it to clean brick.