When I was designing my wedding ring, I ordered small quantities of various white metals to see how they would look in contrast to each other. For the following Hanukkah, a fortnight after the wedding, I used these samples to make gifts for my wife.
For this particular design I took the section of 18 karat white gold square wire I'd purchased for comparison and used it to make a small hoop and a bail. I polished that to a shine and then welded a dome of satin-finished 10 karat yellow gold inside of it. The flat, shiny surface of the wire and the convex, satin surface of the dome create an interesting dynamic, which helps to increase the perceived contrast between the light-yellow color of the low-karat yellow gold and the high-karat white.