Why are green screens only green? If you have ever watched a movie with spectacular visual effects, a TV show with a weather forecast, or a video game with realistic graphics, chances are you have seen the magic of green screens. Green screens are used to create realistic backgrounds and environments that would be impossible or impractical to film in real life. But why are they green? And how do they work? What is a green screen? A green screen is a technique that involves filming a person or an object in front of a solid-colored background, usually green, and then replacing that background with another image or video in post-production. This process is also known as chroma keying , because it involves isolating a single color (chroma) and making it transparent (keying). The transparent areas can then be filled with any desired background, such as a city skyline, an alien planet, or a fantasy castle. This allows filmmakers to create scenes that would be too expensive, dangerous, o...