Lay painters tape along the edges of the brick on both sides of the cement.
Pour 1/4 cup of each of the black, brown, light green and dark green oil-based paint into separate disposable bowls. Dilute the paint by adding 1/4 cup of water to each bowl and mix well with a painters stick or disposable spoon.
Dip the sponge into the black paint and then wring it out, leaving a small amount of paint on the sponge.
Lightly stipple the sponge across the cement in an irregular pattern. You can always add more paint, but cannot remove it once it is applied.
Rinse the sponge thoroughly under clean running water. Repeat the process of dipping, wringing, stippling and rinsing for the brown paint, light green paint and dark green paint. You do not need to allow the paint to dry between layers.
Remove the painters tape before the paint dries and wipe any paint spots or splatters from the brick with a clean, damp rag.