rose gold

Colored gold is the name given to any gold that has been treated using techniques to change its natural color. Pure gold is slightly reddish yellow in color, but colored gold can come in a variety of different colors by alloying it with different elements.
Colored golds can be classified in three groups:
Alloys with silver and copper in various proportions, producing white, yellow, green and red golds. These are typically malleable alloys.
Intermetallic compounds, producing blue and purple golds, as well as other colors. These are typically brittle, but can be used as gems and inlays.
Surface treatments, such as oxide layers.Pure 100% (in practice, 99.9% or better) gold is 24 karat by definition, so all colored golds are less pure than this, commonly 18K (75%), 14K (58.5%), 10K (41.6%), or 9K (37.5%).

View More On Wikipedia.org