First, if you have a color you are automatically attracted to, go with your gut! But if you can’t quite decide, there are a few factors to consider: luster, longevity, price, and weight. The metals are summarized below, but each goes more in depth if you follow the links. You may also be interested in:
Platinum vs. White Gold
Luster, Longevity, and Color
What is the best for a metal allergy?
What are alloys and how are they used in gold?
If you're looking for the best, platinum is your metal. Denser than any other metal used in jewelry, platinum is also the most durable. The stronger the metal is, the more securely it will hold your diamonds as well. Because platinum is naturally pure white, it won't require any plating; its finish is already naturally stunning. It is also hypoallergenic, and the fact that it is tarnish resistant makes maintenance a breeze. Platinum is a rare precious metal – and that's reflected in its price.
In its 24k form, yellow gold is pure. 18k gold gets a quarter of its makeup for a combination of copper, silver, nickel, and zinc. The warmth of yellow gold against the white shine of a diamond makes it a classic pairing for engagement rings.
White gold is blended with copper, silver, nickel, and palladium, and has a white shine that contains more warmth than the silvery glint of platinum. Price-wise, it is more expensive than yellow gold but less than platinum. Most white gold engagement rings are actually plated (meaning coated) with rhodium to make them look more like platinum. This plating typically lasts about 4-6 months, at which point you'll notice the color start to change from pure white back to the natural yellowish-white color underneath. We don't recommend re-plating your engagement ring often; the process requires preparing the white gold first by buffing out all the scratches and polishing it to a high luster before applying the rhodium so it will adhere properly to the white gold. Every time the ring is buffed and polished, a thin top layer of metal is removed from the ring, weakening the prongs and beads that hold the diamonds. Re-plate too many times, and you'll have significantly weakened your ring.
Rose gold is alloyed with copper and comes in shades ranging from a soft, blush pink to a reddish hue. Rose gold can be very complimentary against some skin tones but due to its copper content, it isn't recommended for people with sensitive skin or metal allergies.