Our equivalent of NM in Britain isn't so colorful.
The old 1950s/60s Imperial-size cables were a case of "you can have any outer sheath color you like so long as it's gray."
I'm not exactly sure when it first appeared, but sometime after the switch to metric sizes in the 1970s manufacturers started offering white sheaths as well. They became quite common during the 1980s, especially for exposed surface runs. The clips were then made in both gray and white versions.
With the recent change to the new European color coding for the internal conductor insulation, the cables are back to being available only with a gray sheath.
