The pistachio has a hard, tan shell with a pale green nut. Pistachios have been grown commercially for only 20 years in the U.S., although California is now the second largest producer in the world. Unshelled nuts should have partially open shells and maybe purchased either beige or dyed red. Pistachios are available year-round shelled or unshelled, raw or roasted, salted or unsalted.
Buy unshelled pistachios with shell partially opened. A closed shell means the nut isn't mature. An open shell makes removing the nutmeat easier.