These meaty chiles come from the mountainous regions of Hidalgo and Puebla. When unripe, Serranos are green. When mature they are red, brown, orange, and yellow. They are usually 1-2 inches long and 1/2 inch wide.ÊSuggested Use: Add the serrano to any sauce in which an authentic, hot chile flavoring is desired. Ingredients: Serrano Peppers. Basic Prep: Just add as directed by recipe. Ê Often also spelled Chile, Chilli, Chille.