High Quality Content by WIKIPEDIA articles! The shadow mask is one of the technologies used to manufacture cathode ray tube (CRT) televisions and computer displays that produce color images. Another approach is the aperture grille, better known by its trade name, Trinitron. All early color televisions and the majority of CRT computer monitors used shadow mask technology. Both of these technologies are largely obsolete, having been increasingly replaced since the 1990s by the Liquid Crystal Display (LCD).