You have probably noticed in behind the scenes videos for your favorite movies that many shots are taken against a green or blue screen so that studio shots can be shot as if they were taken outdoors or to place the characters in an alien world. Using this technique yourself in your own video production is actually quite simple, but how do you know which color to choose?
Well the first and most obvious reason is that is there is blue in the shot then you can’t/shouldn’t use a blue screen and the same goes for green. If you use blue/green against a blue/green background then when you or your help is trying to key out the background you will likely remove unwanted elements from the shot.
The second and less obvious thing to consider when choosing which color to use if what time of day is the shot you are using going to be in. For example, being a brighter color, green is much better for day shots because any green left over after the keying will be much less noticeable. This is true for blue screen at night, where left over blue is much less noticeable than left over green.
Check out the video below for some more great information on the topic.