Pink gold is an alloy of gold with copper and silver. Eighteen-karat pink gold is an alloy that is 75 percent gold, 20 percent copper and 5 percent silver.
The copper content adds the rosy hue to the gold alloy, and adding more copper increases the redness in the alloy. Pink gold contains less copper than rose gold (18K rose gold is 75 percent gold, 22.25 percent copper and 2.75 percent silver) or red gold (18K red gold is 75 percent gold and 25 percent silver). If these alloys are 14K instead of 18K, they only contain 58 percent gold.