Anyway, two different designs. First of all I did it with the very desaturated outline as you can see in the first pair. Then I realised that they don't actually have outlines, so I used the border of the coloured segments as a kinda outline. Or something. I don't know how to explain it. But yes. Gems. Multiple colours. And the grey colour was not in any way caused by the fact that my editor just happened to have those colours in the palette at that spot. No. I guess the colour choice was rushed in a way, so it may not be the very best. But oh well.
You know, I don't actually know if gems can look like that.