What is the purpose of a color key?

• A. To isolate and remove a specific color from a video
• B. To synchronize audio with video
• C. To apply a color cast for mood
• D. To adjust the frame rate

Answer: (A)

Color keying isolates a specific color in the footage and makes it transparent, so another background can show through. This is done by selecting a target color (like a bright green or blue) and removing it from the foreground, leaving an alpha channel that reveals whatever is on the layer beneath. This is the core idea behind green-screen work: you shoot your subject against a solid color, key that color out, and replace it with a different background.

This isn’t about syncing audio with video, adding a mood through color grading, or changing the frame rate, which are separate tasks in video production.