I watched a documentary the other night on the Queen Mother. She had the personality to carry off great fashion and jewellery. In 1938, she and the King were due to pay a state visit to France. That was very shortly after her own mother had died and by convention she was expected to wear black. But this was Paris. So on the boat over to France she changed from her black outfit to an almost completely white one, and apparently just wowed the fashionistas. All her outfits for the 4-day visit were either white or cream.
That was a very clever fashion decision. Obviously she couldn’t wear bright colours in order to be seen, but all the white/cream outfits made her very visible.
This blog has more details, though the photographs don’t show her outfits as well as the film in the documentary did:
royalwatcherblog.com/2017/03/16/royal-visit-to-paris-1938/