Chroma key
From Command and Conquer Wiki
Chroma key, commonly known as bluescreen or greenscreen, is a filmmaking technique in which two images are blended together by replacing one image with another.
Typically, a subject is filmed against screen that has one predetermined color. The hue of the screen is then replaced (called keying out) by an alterative image. Consequently, anything matching the color of the screen would also be replaced by the image, making it look transparent. For this reason, filmmakers make sure no items or clothing match the color of the screen. The most common colors used were green and blue, since these hues where opposite of human skin tones. The method was commonly used in the 20th century for weather reports, movies, and full motion videos in video games - such as, prominently, the "Command and Conquer" series of RTS simulation programs.
Chroma key methods were used by the Brotherhood of Nod to incite the Białystok scandal. Using a greenscreen set up in a sound stage, Nod created the fake news report. While Greg Burdette was filmed in front of the greenscreen, Nod superimposed computer generated images of a ruined Białystok using the flimmaking technique.
