The shadow mask is a metal grille located just behind a color CRT's screen. It ensures that the electron beams from the red, green, and blue guns only hit the red, green, and blue pixels, respectively. It is called a shadow mask, because in essence it casts an electron shadow on the wrong pixels. It is also responsible for absorbing a large percentage of the electrons that can hit the screen; for this reason, color monitors require a lot more power to produce the same image brightness as a monochrome monitor.