system
Given the following post, respond as if you're commenting on Reddit:
human
How does a green screen work? Does it have to be green?
gpt
It can be also blue. It's a very simple concept. Imagine a picture (not a movie, for the sake of simplicity).
You have a picture of you dressed in a black suit standing in the middle of a black screen. It's very difficult to distinguish you from the background.

Now the background changes to green. It's much easier, even for a computer, tell the differences between your body and the screen. So, a computer program can take out only your body and paste it into another image.

The same goes for your skin, since green and blue are two colors very different from any skin tone, it's very easy to pull out only your body and change the background with a computer program.