Alloys: Colored Gold
Many alloys of gold are often named by they way they change gold’s coloring, such as rose gold or white gold. This additions can be made to alter the properties - as gold is a rather soft and malleable metal - and often is done so for aesthetic reasons. Most forms of colored gold are used in jewelry or decorative items, with a few exceptions.
As gold is one of the few metals that exhibits color (along with copper), additions of other elements to gold can alter the structure ever so slightly in a way that alters the light reflected.
Colored gold alloys tend to fall into three main categories: those within the Au-Ag-Cu system (such as in the phase diagram depicted above); intermetallic compounds, and surface oxide layers. Perhaps the most common and well known varieties of colored gold include white gold and rose gold, but there are many others, including red, pink, green, blue, purple, and black: