When people talk about koi, they're most likely referring to the Gosanke family of fish. This group includes the popular red and white Kohaku koi, which have been bred for centuries in Japan to feature specific patterns. Koi living in the wild usually sport demure brown scales, which make them indistinguishable from most carp species. Rarer varieties are yellow, blue, or cream. Posters depicting these fish add a traditional flair to any decor.