During the initial period of koi breeding carp mutations, Japanese koi hobbyists could only produce varieties with one or two colors. Over the years as this practice has grown popular, the assortment of colors on the koi fish has increased and more pattern combinations can be seen. Some colors that are usually seen are red, black, blue, yellow, and white koi.

To be able to recognize different varieties of the colorful koi fish, it is important that you have a firm understanding of its many classifications and how they are grouped. Although there may be certain standards that each classification is required to have, the diversity of patterns among these fish will vary. Examples of some popularly known koi fish are Kohaku Koi that are seen as white koi fish with red markings, and Hikarimono (or Ogon) that are metallic koi seen in singular color that vary among gold, platinum, or orange.

The name hikarimono came from the word "hikari" that means "metallic" and "mono" that literally means "one" (that pertains to its color). Hikarimono, also known as Ogon varieties that are most commonly seen are the metallic white or platinum, while some that are yellow known as Yamabuki Ogon can also be seen. For this type of koi, their color should be of equal hue from head to tail, right down to the tips of their fins. Large fins on Ogon koi are often preferred to the offset the appearance of a plain body.

The Platinum Ogon or White Koi is a very popular fish and considered to be a unique variety of the koi fish. When these fish move, their scales appear to shine with the same luster as that of a precious metal. Their first appearance was seen in 1963, by crossbreeding a Kigoi with a grayish silver Nezu Ogon. Often, the Platinum Ogon are placed on ponds that are dark or murky since their metallic sheen is a perfect contrast to the environment. This type of Ogon is considered to be quite hardy and they grow rapidly.

Today, most Platinum Ogon are bred with varieties of the GinRin to create scales that appear even shinier since the scales of the GinRin are quite unique and very different from the common metallic koi. GinRin have sparkling, glittering scales much like cut diamonds instead of the smooth, metallic scales of the Ogon. Crossbreeds between these two types of koi are commonly called GinRin Ogon. Keep in mind that when attempting to crossbreed, proper care should always be taken to ensure breeding in a clean and healthy pond environment to avoid any unnecessary infections or complications.

The growing popularity of koi hobbyists is mainly due to the fact that there is a large variety of colors that they can choose from - endless possibilities can occur when breeding. The majority of the pigments of these koi fish are located on the top area of the fish. When seen in a pond, viewed from the top, it is where their colors are best shown off - especially when reflected by natural light.