thanks ....... as we know, S. & F. were agents, wholesalers and importers, and although they may well have sold British made insulators
there is always the possibility that some of their designs for such items might have been manufactured outside the U.K. ........... that is unless the U.K. was the only country that made piano feet. Unfortunately, their catalogue doesn't provide specific information on origin.
In theory British made patterns of insulators made during the period 1842 to early 1884 should carry a lozenge, so assume that no one involved with the GMB has yet found one with this particular set of Registration details, otherwise it would probably have already been posted.
I think you're right about the colours - most designs for these things seem to turn up in the usual variety of greens, blues, uranium and flint.