Interesting to note American TV was filming stuff in colour long before the majority of people could receive it. Although as noted in the thread comments on the 1958 clip, President Eisenhower can be seen on tape in colour, whereas there appears to be little or no colour video at all of JFK save for possibly that clip that showed him being shot, said clip turning up years after the event.
When it came to NBC, it's hardly suprsing. RCA was their parent company, they developed the NTSC colour standard, and I think manufactured most colour sets at that point in time, and I think got money from ones made by other maufacturers too, so you can understand why they pushed colour.
It's also the reason ABC and CBS dragged their heels somewhat-, ABC didn't start until 1962 and CBS didn't have any regular colour programming until 1965 (even programmes made in colour, like The Lucy Show, were shown in black & white before then), they wouldn't be wanting to do something which would help a competitor. CBS were probably even more bitter as they developed a colour standard which was initially adopted in the early 50s, then quickly dropped, which is why were so late compared to the other networks.