I'm not really clear, by your description, what you are aiming for
---but I gather that it's essentially 2 or 3 colored bands stuck
together - a wedding band that is 3 "stripes" going around? One
piece of advise- make the bands first, and then solder them together.
But- in the "industry" - people like Stuller - those rings aren't
soldered at all. Sometimes they do things like put them each on a
rotating spindle, going opposite directions, and drive them together,
and the friction fuses them. More often, they are fused together
just like Mokume'. That's why they're so neat - no solder, perfect
fit, since they are made in a machine shop. Besides other sources,
the inimitable James Binnion knows everything about Mokume'. He has
messages lately, here in Orchid.