Chroma key is the ability to combine several layers of video in one frame at once. The subject is placed in the frame against the background of a plain canvas, most often green or blue. This background is called a chroma key on set.
This mod is useful for those who want to take a photo or shoot a video in GTA San Andreas without third-party items. Your background will be green. There will be no shadows in your frame. You can find a chroma key at the Los Santos airport, or enter the "CHROMAKEY" cheat. To disable, you also need to enter it. The standard size is 20x20x10, but you can change it in the INI file.