Username1, the problem with the mechanical (disk) system was picture quality. It was only 30 line resolution.
The Trinoscope was only to demonstrate color TV - RCA never considered selling it. At the time they were developing the tricolor tube, which they thought would be the solution.
There are several one gun color tubes, starting with a 1951 prototype:
http://www.earlytelevision.org/rca_d...al_onegun.html
Later attempts included the Philco Apple and Uniray:
http://www.earlytelevision.org/apple_crt.html