The container on the left shows how much water is used if one turns off the water while washing their hands. The container on the right shows how much water is used if one lets the water run while washing their hands.
Green is obsessively turning off the water. By obsessively turning off the water, you save water which makes for a green, healthy planet and you save on those green slips of paper we all like to accumulate. Read my Suite101 article "How to Save Water in the Bathroom" for a better way to wash your hands.