1953 NTSC Color Gamut

[ppppenguin]

That's a pretty comprehensive summary of the issue. The only thing missing is WHY the reference primaries were changed. AFAIK it's because the original NTSC phosphors resulted in pictures that weren't very bright. Newer phosphors were brighter but couldn't give the same range of colours. Since the new colour gamut was good enough it became the standard.

By the time of PAL and SECAM all this had more or less settled down. Not quite though. There was a set of EBU reference primaries that turned out to be expensive and/or hard to make as phosphors. So in practice most CRTs had slightly different primaries. AFAIK it was only a small difference and didn't really matter outside of very critical colour matching.