Kohaku are white koi with red markings. The white should be snow white and the red should be thick whether it is the hard red from purple or orange color that is referred to as persimmon. It is said that the persimmon red/orange is more stable. I’ve read many times in many places “Koi begin and end with Kohaku”. The Kohaku is the most popular class with the high end hobbyist. Kohaku were the first variety to become stabilized and there has been more effort put into breeding and improving them than any other. The red should not go below the lateral line of the Kohaku.