Eat out in New Mexico and you’re bound to hear it sooner or later: “Red or green?” That’s the state’s official shorthand for “what color chile would you like slathered on your burger or burrito?” You can go the iconic route and ask for green, or get maximum kick by requesting both: “Christmas, please.” 

Red, green, or in between, chile is New Mexico’s pride and joy. What kind of pepper are we talking about here, and what causes a single plant to come in two distinct colors?