Ancho chiles are a type of dried chile pepper commonly used in Mexican and Southwestern U.S. cuisine. The pepper is the dried version of is the poblano pepper—to be specific, it's the dried version of the ripe version of the poblano pepper.In other words, the chiles we know as poblano peppers are fresh chiles that are harvested before ripening, which is why they're green. It's what your basic chile relleno is made with. But when allowed to ripen, poblanos turn red and develop additional sweetness, which in turn balances out their already mild heat. Thus anchos are red while poblanos are green.