Green is the color of nature--it's the color of ecology and peace, and is an extremely important color in almost any watercolor.
Originally, Sap Green was made from the berries of the buckthorn plant fixed on a substrate of alum, but as you might guess, it was not very colorfast. Winsor and Newton, a premier manufacturer of watercolors, offers this beautiful convenience mixture, Permanent Sap Green. This pigment is a yellow green with just a touch of blue in it to dull it down a little. Permanent Sap Green is quite light valued. It's lightfast and transparent, and is staining, as all transparent colors are. This is a color that is easy to use, mixes easily, and provides a more natural look for foliage. W&N Permanent Sap Green blends easily and almost any color can be used to shade it.