Mokume Gane has probably been invented by the armourer Denbei Shoami (1651 - 1728) who lived and worked in the Akita prefecture in northwestern Japan. He was said to be an excellent artisan and got the permission to use the name Shoami (from the Shoam school formed in Kyoto at the end of the 16th century; "shoami" usually is translated as "one who is talented in arts"). Initially, Shoami called his technique Guri Bori since the pattern of his first Tsuba (the round, or occasionally squareish, guard at the end of the grip of japanese bladed weapons) looked like Guri which is a Tsuishu technique of carved laquerware originating in the ancient China. Tsuishu is a technique which generates patterns by engraving thick coatings of different laquers. If this leads to lined patterns, it is called Guri. Later on, Shoami named his technique Mokume Gane (from "mokume" which translates to "wood-grained" and "gane" which translates to "metal"). His oldest known work is a part of a Kozuka (a small knife, often used as a throwing weapon) where he used sheets of gold, silver, shakudo and copper for the grip. These sheets have been fire-forged together.
For a long time, japanese craftsmen already knew of and used many differently coloured alloys, especially shakudo and shibuichi. Shakudo is a copper alloy containing approximately 4 percent of gold while shibuichi is another alloy made from copper and silver. Using certain patinas, these metals can be coloured as well.
These well-known japanese copper alloys are used for Mokume Gane until today. However, it is important to mention that these materials may change their colour due to oxidation; they might as well colour the skin on direct contact. Therefore, combinations of precious metals are usually used for Mokume Gane which has direct contact to the skin (like red gold, yellow gold, platinum and silver). Additionally, palladium is often used as well since it is also resistant to oxidation and can be bonded pretty easily with precious metals. Especially for wedding bands, copper alloys are virtually never used at all since they very often leave green skin (basically, this is copper rust as known from copper-made rainwater gutters). For other pieces like belt buckles, bracelets, cuff links etc, such alloys can be certainly used. Even for pendants, these materials may be used if the construction makes sure that the copper alloys do not touch the skin as far as possible.
Obviously, Mokume Gane made from precious metals does not change its colour - actually it is made from the same materials known to be used for classical wedding bands and other jewellery. Likewise, the durability of jewellery pieces or wedding bands made from Mokume Gane is not different to usual pieces. Though silver is known a a relatively soft metal, this does not preclude its use in Mokume Gane materials. The same piece made from Mokume Gane is actually often much harder than a usual gold ring or silver ring due to the heavy forging processes during production.
At Unikatschmuck, you find pieces of Mokume Gane jewellery both from precious metals and from these classical copper alloys. Usually, materials are used which show a lot of contrast in colour, for instance, silver and palladium (white-gray), silver, yellow gold and palladium (white-yellow-gray), green gold and palladium (greenish yellow-gray) or red gold together with other materials. I can also offer four-colour combinations (red and yellow gold, silver and palladium) and even rare combinations like platinum and yellow gold. If technically possible, I always try to satisfy a customer's desire for colour combinations.
The patterns are equally important in Mokume Gane pieces. Get some inspiration from the picture gallery above - virtually every pattern can be done starting from seemingly random patterns to finely defined markings (a particularly good example is the belt buckle with the gecko design). The pattern of each single piece is always defined together with the customer. Nonetheless, each single piece of Mokume Gane is always unique since the patterns can never be exactly reproduced.