Mix the first coat of stucco, the scratch coat, in a large bucket with an electric drill and paddle-bit attachment. Pour 1 part portland cement and 2 1/4 to 4 parts sand into the bucket. The amount of sand determines the smoothness of the texture -- the more sand, the greater the texture. Add water slowly, and stir with the paddle until you have a thick paste suitable for spreading on your surface. Apply with a trowel, and then scratch the coating with a mason's scratcher to help the top coat adhere.
Measure out the amounts of portland cement, sand and water that you're using to create the stucco for the top layer, which contains the color. This coat, known as the brown coat, requires 1 part portland cement mixed with 3 to 5 parts sand. Figure out how much pigment you want to use, as well. The maximum amount of pigment by weight is 10 percent of the weight of the cement. Check the bag of cement for the weight of the material. The more pigment, the deeper the color.
Mix the brown coat of stucco in the large bucket, using the electric drill with paddle. Fill the bucket with about 75 percent of the water you're using to create the amount of stucco you're mixing. You can determine the amount of water needed by the amount of cement used. Read the cement manufacturer's instructions for appropriate amounts.
Add 50 percent of the sand to the water, all of the pigment and all of the portland cement. Mix thoroughly with the paddle, and then add the remaining water and sand. Continue mixing until your stucco is a smooth, spreadable consistency. Mix five minutes more, and then apply the mixed stucco to your surface.