Silver is more abundant that gold and occurs naturally in its pure form, as an alloy with gold and other metals and in minerals.
Yellow gold is the purest color of all the colored golds, as the mineral looks golden (yellow) when mined. It is the most hypoallergenic of all the gold colors and requires the least amount of maintenance of all the gold colors.
White gold is an alloy of gold and at least one white metal. In order to make the gold white, it is combined with metal alloys that are white in nature and plated with an extremely hard element called rhodium.
Platinum is considered the most valuable metal in jewelry today due to its strength, purity and rarity.