Even in the UK, iut is no longer acceptable to over-sleeve a G/Y-insulated conductor. That used to be allowed for multt-core, but not single-core cables, but that is no longer in the case.I happen to live in a country where over-sleeving isn‘t allowed either (at least for earth, neutral is a bit of a grey area) ...
However, BS7671 has no problem with any other over-sleeving (just at terminations), although I think that it does say that it is 'preferred' for insulation colour to be the same throughout the length of the cable.

