Things You'll Need
Mop and bucket of water
Dyes do not penetrate deeply into concrete, so they enhance rather than hide concrete's natural variations. Since the chemicals in dyes do not break down any of the ingredients in concrete, you can apply dyes without worrying about causing any damage. The product comes in either a premixed liquid form or a powder that you must mix with a solvent, such as acetone. Mix dyes at full strength for darker colors or diluted for lighter tones.
Clean the concrete surface of all dirt and dust. Sweep the floor, vacuum around the edges where a broom may not reach, and go over the floor with a wet mop. Allow the concrete to dry completely.
Don a pair of rubber gloves and mix the dye and solvent in a plastic bucket. Follow the dye manufacturer's instructions regarding the type of solvent needed and the ratio of dye to solvent.
Pour the dye mixture into a paint sprayer. Choose a sprayer that has seals and spray tips that are listed as safe for acetone or the type of solvent you use.
Spray the floor with dye. Move the sprayer wand in a circular motion while keeping the tip about 2 feet away from the surface.
Allow the dye to penetrate into the concrete, which takes only about a minute. Sponge away any excess dye that may have puddled, if you're using a water-based mixture.
Apply a second coat of dye after letting the first coat dry for about 15 minutes. This is an optional step if you want to darken the color or if you want to create patterns in the surface.
Seal the dyed concrete surface once you have finished coloring it. Seal the floor after allowing the dye to dry completely for several hours. Spray the sealant -- typically a polyurethane -- using a sprayer with hoses and tips suited for sealants.
Allow several more hours of drying time before moving in furniture and walking on the floor.
Concrete that is several years old will have accumulated dirt, and maybe some stains. Unless you feel that those elements add character to the concrete, you may want to try a deeper cleaning than just sweeping and mopping. Choose a concrete cleaner and give the surface a good scrubbing. Also, if the concrete was previously sealed, you must remove that material using a stripper before applying dyes.
Use caution when working with acetone-based products. Increase ventilation by opening all the windows in the room, and ensure that no sparks or open flames are near the solution. Acetone is highly flammable, and its fumes are noxious.