There are a lot of similarities between white and yellow gold — both work well with nearly any cut, clarity, and carat of diamond. The main difference between white and yellow is simply the metal mixture that’s used to make them. Some of the most common metals used to mix with gold are copper, silver, nickel, palladium, and zinc. Depending on what metals are used and the percentage that they’re present will result in these two common colors. White gold has more nickel and zinc, while yellow gold contains more copper.
However, it’s the karat number that you should be looking at if you’re concerned about the presence of pure gold. 18 karat yellow gold and 18 karat white gold have the same percentage of gold, plus 6 parts of ‘other metals’ (totaling 24 karats).