Fascinating. Looking at the photo I mentioned (it’s an Adrian Balch collection image) it does appear to be grey rather than weathered metal. Its of XM706 and taken in 1970.

The characteristics of dayglo do mean for a lot of variation, not just because of film, lighting or fade, but also thickness of the paint, the sort of undercoat used and so on. It is good to have the use of various shades confirmed.