Put a handful or two of sand into a plastic bag with a zip-lock top. Add drops of food coloring to achieve desired color. Securely close the first bag and then double-bag it in case the first bag tears. Shake the bag to distribute the color. Repeat for a few different colors. Let the sand dry overnight, or at least for a few hours. Choose an attractive container to hold your sand. Used jars or old vases work well. It looks nice to layer the different colors of sand on top of each other. You could also mix all of the colored sands together.