Pistachios are sometimes dyed red or green in order to increase their eye appeal, but the so-called nuts themselves (they're actually seeds or "drupes") can appear slightly green or even reddish in nature as well. The largest American source of pistachios is California, but the biggest producer in the world is Iran. Pistachios are grown and enjoyed all over, however, and actually look to be pretty pleased with themselves, if the tendency known as pareidolia has anything to do with it. (Another nut-like example of this is the little bearded man you can see if you carefully split apart the two halves of a peanut.) According to Food Editorials: "Pistachios are joyful. In China people refer to them as 'happy nuts' while in Iran they are known as 'smiling nuts.' Middle Easterners call the pistachio the 'smiling pistachio.' In these countries, if you hear the pistachios shells opening on a tree while you are resting beneath it, it is considered good luck..." Pistachios are also unique in that they can be roasted and salted while still in the shell. Though it's possible to buy them already shucked (probably the best way to observe their natural green color), I've often thought it just as well that they generally come in those little beige shells (which can then be saved and used for any number of things, including craft projects and slug deterrents in the garden), if for no other reason than that it inhibits overeating. (Especially if you're as nuts about nuts as I am). In fact, in 2008 Dr. James Painter of Eastern Illiniois University came up with something called the Pistachio Principle, which basically says that "the act of shelling and eating pistachios one by one slows one's consumption, allowing one to feel full faster after having eaten less." Getting back to whether or not the word pistache means the color of a pistachio (or is even an English word at all), I actually couldn't find much confirmation of that beyond the dictionary I consulted the other night at a friend's house. But marginal though it may be, I like the word anyway; it's like pastiche with the first two vowels reversed. Which puts me in mind of the movie Great Expectations with Ethan Hawke. That film had so many shades of green in it (a veritable pastiche of pistache) that upon seeing it in the theater in 1998, my friend and I thereafter dubbed it "Green Expectations." There were 25 cases of Princple* found in OhioLINK today, and 157 in WorldCat.
(Pistachio Tree at Château Noir, by Paul Cezanne, at the Art Institute of Chicago, courtesy of Wikimedia Commons.)