The first two words in the name of every koi indicate the coloring of the koi. Every Koi is differentiated by a pattern created by those two colors. There are 30 primary colors and 30 secondary colors. Certain colors and color combinations are rarer than others. The rarest color combination for every breed is the Black Night.
The Koi Log, accessed through the menu, records all koi owned at any time, their age in days, and their rarity ranking out of 28,800.
There are 28,800 possible breed and color combinations, out of which there are 900 color combinations for each breed. Some color combinations are higher in ranking than others of rarer breeds: for example, although the Cosomi is a rarer breed than the Bekko, the Black Night Bekko is higher ranked (26,617) than the Cream Ash Cosomi (27,324).
The 30 primary colors are as follows, from most common to rarest.
The 30 secondary colors are as follows, from most common to rarest.