Add one part portland cement, three parts fine sand and concrete colorant to a mixing trough. Pour in small amounts of water and mix it together with a trowel until you achieve a peanut butter consistency.
Place the mold on a work surface and spray the inside with an even coating of mold release spray. This will allow you to remove the stepping stone from the mold with ease.
Pour the cement mix into the mold a little at a time. Pat down the cement with your hands as you pour it into the mold. Continue adding cement until the mold is full. Smooth over the top surface with a trowel. Tap the mold against the work surface to help remove any air bubbles from it.
Allow the cement to dry between three to six hours. Remove the stepping stone from the mold and let it sit out for 24 hours. Mist the stone three times during the 24 hour period with a spray bottle of water.
Place the stone in a plastic bag and allow the it to cure for at least one week. Remove the stone from the bag. Allow the cement to continue curing for approximately one month before stepping onto it.