Metal: Niobium

Niobium is a pure metal, not a precious metal but like titanium takes colouration well, in its raw form it is a grey and not very appealing - but once heat and electricity are applied to it in the process of anodization the surface will colour permanently (though this is a thin layer and will wear off eventually or if scratched persistently).
As this is a pure metal it is ideal for those with sensitive skin types, however due to the fact that it isn't very hard wearing (at least the surface colour) we usually use it only for decoration where will come into very little contact with anything else. That said, if you are really concerned, we can use it for ear-wires at your request.