The CBS system in 1946 used 525 lines, 24 fps. There was a problem with flicker with moving objects, causing color fringing. In 1950 CBS changed to 405 lines, 24 fps in order to fit into a VHF 6 mHz channel.
We have working 405 line CBS field sequential receivers at the museum, and they produce wonderful color with slow moving images.
CBS did broadcast to the public in 1951 for a few months. Here is the story:
http://www.earlytelevision.org/cbs_color_system.html