The first choice you must make is one of color. This selection usually depends on personal preference, skin tone, and the color of other jewelry you may own. Remember when considering yellow gold that it is available in several different hues, which include a greenish-yellow and a pinkish-yellow.

Yellow gold
If your choice is yellow, the only decision you must make is whether you prefer 14K or 18K. 14K gold is more affordable and harder. 18K gold has a richer and brighter color.
If you prefer a white metal, your choice may be more difficult. White gold and platinum are distinctly different metals.
Advantages – The most lustrous of all metals. Prongs in yellow gold are easier to set. Yellow gold helps “disguise” off-color diamonds, and heightens the purity of warm color gemstones such as citrines, rubies, and garnets.
Disadvantages – Yellow gold could influence the appearance of high color diamonds making them appear yellower. It could also influence the purity of cooler color gemstones such as sapphires, rubies, and garnets.

White gold
Advantages - Harder and more resistant to scratches than platinum. Also much more affordable.
Disadvantages - Discolors to yellowish-white with wear as rhodium wears off. It is also more brittle which may result in broken prongs and cracks in the shank.

Platinum
Advantages - The noblest of metals, more precious and purer than gold. An excellent stone holder as prongs more easily conform to gemstone. It is also much easier to do pave work in platinum. Platinum jewelry does not discolor with age and its shine is easily restored by high-speed buffing. Platinum does not wear away. The metal is simply pushed and displaced so mountings hold up and last longer than gold.
Disadvantages - Much more costly than gold and more dense in weight. Higher cost means generally a smaller selection to choose from. Platinum is more easily scratched and repair costs are higher.