At a concert at the Barbican in 1985 Princess Diana wore a burgundy coloured dress with the amethyst earrings and the pearl and amethyst bracelet.
In Canberra in November 1985 she also wore the amethysts with a burgundy coloured dress. I think that the colour of the amethysts is clearer in this photo.
But the amethyst colour is not as clear in this photo.