Wikipedia
Telechrome was the first all-electronic single-tube color television system. It was invented by well-known Scottish television engineer, John Logie Baird, who had previously made the first public television broadcast, as well as the first color broadcast using a pre-Telechrome system.
Telechrome used two electron guns aimed at either side of a thin, semi-transparent mica sheet. One of the sides was covered in cyan phosphor and the other red-orange, producing a limited color gamut, but well suited to displaying skin tones. With minor modifications, the system could also be used to produce 3D images. Telechrome was selected as the basis for a UK-wide television standard by a committee in 1944, but the difficult task of converting the two-color system to three-color RGB was still underway when Baird died in 1946.
The introduction of the shadow mask design by RCA produced a workable solution for color television, albeit one with considerably less image brightness. Interest in alternative systems like the Telechrome or Geer tube faded by the late 1950s. The only alternatives to see widespread use were General Electric's slot-mask, and Sony's Trinitron, both were modifications of the RCA concept. All CRT-based methods have since been almost completely replaced by LCD television, starting in the 1990s.