The primary difference between red and green Hatch chiles lies in their ripeness and flavor profile. Both types of chiles come from the same Hatch chile plants, but they are harvested at different stages of maturity. Green chiles offer a fresh, crisp, and spicy kick, while red chiles provide a deeper, sweeter, and smokier profile with less heat. Some recipes call for green, while others call for red, but the choice is ultimately a matter of personal preference and the flavor profile you're aiming to create in your dishes.