Here is a world wide list of standards.

Pre colour the frame rate was locked to the mains. This meant that any mains derived hum or interference was stationary on the screen and so less visible. With the advent of colour the frequency stability needed for the chrominance subcarrier was higher than could be derived from the mains standard. The master frequency became the chrominance subcarrier. The mains was no longer used as a reference although the same nominal 50Hz standard was used. PAL had advantages where signal was weak and multipath reception was a problem.

Flicker was more of a problem because of interlaced scanning. The picture repetition rate was 25 Hz in two successive field scans of 20ms each. This produced a 25Hz flicker that could be particularly evident on CRT displays where the glass bent over at the top of the screen, producing a magnified image.

Stu