You can make your own custom color chalkboard paint by following these instructions from Lowes Creative Ideas magazine.
To make custom-colored chalkboard paint, pour 1 cup of satin latex paint into a container. Then add 2 tablespoons of white unsanded tile grout. Using a paint stick, mix thoroughly. If the mixture becomes too thick to brush on, add a tablespoon of water, and mix again.
I love this idea of writing on flowers pots, this would be really cute for herbs.
Melinda