- blue
Aka - red
Bu - size classification
Budo - purple
Cha - brown
Doitsu - German scale, these are either completely scaleless or have rows of large scales along the dorsal and lateral lines
Gin - silver
Hi - red
Kana - male koi
Ki - yellow
Kin - gold
Mena - female koi
Midori - green
Nezu - gray
Orenji - orange
Shiro - white
Sumi - black
Tategoi - small koi with potential

Color Patterns
This list gives some of the more notable patterns.

Asagi - body has blue-gray reticulated scales with a red underside and red in the pectoral fins. The head should be an unblemished pale blue.
Bekko - koi with red, yellow, or white background with black spots running down the back.
Goshiki - literally meaning five colors (white, red, black, blue, and dark blue.) Usually a white body with blue reticulated scales which is overlain with a pattern similar to a kohaku or sanke.
Hariwake - platinum body with patterns of orange or yellow.
Kawairmono - this is a term for recognized patterns that do not fall under one of the major pattern types.
Kohaku - white body with patterns of red
Koromo - white body with blue or black pinecone scales over red patterns
Kumonryu - doitsu koi, white body with patterns of black
Matsuba - pinecone pattern over whole body
Ogon - solid color koi
Sanke - white body with patterns of red and black, there can be no black on the head.
Showa - black body with patterns of white and red
Shusui - doitsu koi, white body with blue scales along dorsal line and a red underside
Tancho - solid white body with a red circle on the head.