Sometimes an aluminum project needs to be darkened in order to give it a cool, gunmetal gray look. Anodizing, staining, then sealing the aluminum is the typical way to get the color darker. If you have the materials, another way to is using a chemical or physical deposition that puts a special layer on top of your piece that blackens the aluminum. For more aluminum darkening tips, click here:: Safest Way to Darken Aluminum?