Hikarimuji (hee-KAH-ree-MOO-gee) is a classification that incorporates metallic, single-colored koi, which can come with or without scale reticulation. The classification (also denoted as Hikari Mujimono) designation comes from “Hikari” meaning “shining” or “metallic” and “Muji” which is quite simply “plain” or “solid.”