Original black and white NTSC television was 30fps interlaced. You got a half frame, every other scan line, every 60th of a second, so a full field was painted every 30th of a second. Why 30 instead of 24 like film? Because US electrical power is 60Hz. That could be used as a convenient timebase to sync signals with.

Adding color to that existing standard while still maintaining compatibility with existing black and white TVs was doable by very slightly decreasing the frame rate to 29.97, which was within the vertical sync tolerance of a television. worst case scenario you'd have to slightly turn the V Hold knob on the back of the TV set. The only 20th century analog video tech that was truly 60fps color video was VGA, a true RGB signal which AFAIK was never sent over the air.