Proper noun
English Wikipedia has an article on:Rainbow BooksWikipedia
Rainbow Books pl (plural only)
(computing) The various standards for CD formats, each named after a particular color.
Meronyms: Red Book, Yellow Book
Earlier this spring it revealed it had purchased used bookseller Rainbow Books, and on Wednesday it announced the full-fledged launch of its publishing arm, Rediscovered Publishing, with the upcoming release of a children's book,… Source: Internet