Fine or sterling silver for enamelling plique-a-jour

[As3fthjkl]

heyo, wasn't really sure which forum to post this in so please tell me if im wrong but for the more experienced enamel artists out there i was wondering if for plique a jour i should do fine or sterling, in my practice my sterling silver attempts all turned the enamel green even thought i bought clear enamel so im not sure whats going on there but i was wondering if it would have anything to do with the copper quantity in the silver?

i also have a follow up question, im doing research for a future massive project of mine and i want to make sure i have every type of enamelling techniques, does anyone know if im missing some? here is the list i have currently;
plique-a-jour, cloisonne, grisaille, champleve, limoges, basse taille, camaieu, sgraffito, scrolling, raku, and fume.
i feel i am definitely missing some, any knowledge on more is greatly appreciated.

all the best,
Gyn