AJM has an article in the July issue on various colors of gold. Thearticle, by Chris Corti, describes how each color is achieved and itsqualities, such as workbility. The article is currently availableon-line at the AJM web site at http://www.ajm-magazine.com.
The way they get the blue color on 14k gold is by using iron, and Idon't know what % iron is used.
Billy S. Bates