 "Rainbow" was released on 18 December 2002 by Avex Trax.It was released in Taiwan by Avex Taiwan and in China by Avex and the China Record Shanghai Corporation (CRSC).The promotional photography, directed by Shinichi Hara and photographed by Leslie Kee, features a blue-hued Hamasaki sitting in water with rainbow-colored extensions in her hair; her name and the album title is featured at the bottom.