Instead of trying adjustments piecemeal, I would recommend working through the setup procedures described in the service manual. This article has a link to the 91-page RCA manual:
http://antiqueradio.org/RCACTC-4ColorTelevision.htm
Those procedures include purity, convergence, tracking, color AFC, etc. Follow the order given in the manual. First, as noted, make sure you have a good "black and white" picture. Then comes purity, and so on.
There's a reason why the factory doc describes this stuff in detail and in a particular order. The complete setup on an early color set is not something that the average consumer could "eyeball" by whipping out a screwdriver and turning random adjusters for a minute or two.
If you're patient and your TV is in good shape, the CTC-4 will reward you with a very nice color image.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html