色键技术是从素材中删除背景并露出后面的另一个素材，已被很多领域大量使用，尤其是电影、影片、游戏行业。色度键控技术常用于影片的后期制作。这种技术也称为色度键控，或由于各种具体颜色变化的术语如绿幕、蓝幕。色度键控可以是任何有均匀的背景，但绿色和蓝色背景更常用，这是因为它们与大多数人的皮肤颜色存在最明显差异。在拍摄过程中，要尽量防止演员的服装或任何部分与背景颜色重合。

比方说天气预报，其中一个节目主持人在电视中显示为站在一幅大的地图前，期间在现实中地图是一个大的蓝色或绿色的背景。当使用一个蓝色背景时，所有蓝色的部分都会转化为地图。如果节目主持人穿蓝色的衣服，他的衣服也将被替换成地图。

Chroma key compositing, or chroma keying, is a special effects / post-production technique for compositing (layering) two images or video streams together based on color hues (chroma range). The technique has been used heavily in many fields to remove a background from the subject of a photo or video – particularly the newscasting, motion picture and videogame industries. A color range in the top layer is made transparent, revealing another image behind. The chroma keying technique is commonly used in video production and post-production. This technique is also referred to as color keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate a color used in the background.