The Jargon File (version 4.4.7, 29 Dec 2003):

book titles


    There is a tradition in hackerdom of informally tagging important textbooks
    and standards documents with the dominant color of their covers or with
    some other conspicuous feature of the cover. Many of these are described in
    this lexicon under their own entries. See Aluminum Book, Camel Book, 
    Cinderella Book, daemon book, Dragon Book, Orange Book, Purple Book
    , Wizard Book, and bible; see also rainbow series. Since about 1993
    this tradition has gotten a boost from the popular O'Reilly and Associates
    line of technical books, which usually feature some kind of exotic animal
    on the cover and are often called by the name of that animal.


The Free On-line Dictionary of Computing (30 December 2018):

book titles

    There is a tradition in hackerdom of informally
   tagging important textbooks and standards documents with the
   dominant colour of their covers or with some other conspicuous
   feature of the cover.  Many of these are described in this
   dictionary under their own entries.  See Aluminum Book,
   Blue Book, Cinderella Book, Devil Book, Dragon Book,
   Green Book, Orange Book, Pink-Shirt Book, Purple Book,
   Red Book, Silver Book, White Book, Wizard Book,
   Yellow Book, bible, rainbow series.

   [Jargon File]

   (1996-12-03)