The most common grades of gold, in addition to pure 24K, are 22K (92%), 18K (75%), 14K (58%) and 9K (38%).
18K white gold and 18K rose gold are all the alloy that consisted of 18k gold and other elements in various proportions. The reason why the color is different because they join the other 25% proportion of the different metal .18K platinum, also known as 18K white gold; adding other elements of 25% proportion , such as silver, palladium, zinc, nickel, etc.; 18K rose gold is the inclusion of 25% proportion of platinum, copper, etc.; 18K gold add 25% proportion , such as silver, copper, aluminum, etc.
The popular one is rose gold among the alloys,it is fairly unique in appearance, as if the rose in golden sunshine, gold rose in the band, very special. The highest karat version of rose gold is also known as crown gold, pink gold ,which is 22k pink gold may be made of 25% copper and 75% gold. For 18k rose gold, typically about 4% silver is added to 75% gold and 21% copper to give a rose color. 14k pink gold is often found in the Middle East and contains 41.67% copper.