I’ve been away for a while and have missed the beginning of this post.
Liver of sulphur works well, but is not resistant to abrasion. Ths
surface produced by immersing the silver in Zinc Chloride (3% Soln) is
much more robust and can even be polished lightly with rouge.
For other surface colours, including a remarkable turquoise (!), see
Michael Rowe, The Colouring, Bronzing and Patination of Metals,
Published by Thames and Hudson. My copy is never on the bookshelf.