Today, pistachios remain one of the most popular nuts for people of all ages. Pistachios or Green almonds as they are sometimes called are popular because of their small size, green colour and easy to open shells. Pistachios are grown on trees and have naturally tan shells. The kernels inside the shells are a greenish tan. They get their greenish coloring from chlorophyll. Chlorophyll is a natural pigment that gives leaves their green color.