Zenith Color
It should be noted as Norgeway correctly pointed out, Zenith did indeed design their own circuitry, as they did not want to license RCA's design. As a result, Zenith's color de-modulator circuit was a poor substitute to RCA's and as such produced inferior color.
It was a stupid decision, as Zenith, in all other ways, made a very fine television set - oh yeah - except for their ingenious but ultimately stupid Space Command wireless remote control. Ingenious in that it required no batteries; stupid in that all their remotes only allotted three sound levels, seemingly none correct. And their pinnacle remote, the Space Command 600, five-function remote (whoops, that's seven if placed in mute) was a bit of a joke even back then as the added two functions - the tint up down control, moved in steps, again often none correct. Also, common to all units, the relatively small spring wires, supporting the tuned rods which provided the individualized signals for each function, often broke, rendering one or more functions intermittent or useless.
But it was part of an exciting new technology back then and who am I to complain? (Color de-modulator circuit, notwithstanding).