The Collaborative International Dictionary of English v.0.48:

Blue \Blue\ (bl[=u]), a. [Compar. Bluer (bl[=u]"[~e]r);
   superl. Bluest.] [OE. bla, blo, blew, blue, livid, black,
   fr. Icel.bl[=a]r livid; akin to Dan. blaa blue, Sw. bl[*a],
   D. blauw, OHG. bl[=a]o, G. blau; but influenced in form by F.
   bleu, from OHG. bl[=a]o.]
   1. Having the color of the clear sky, or a hue resembling it,
      whether lighter or darker; as, the deep, blue sea; as blue
      as a sapphire; blue violets. "The blue firmament."
      --Milton.
      [1913 Webster]

   2. Pale, without redness or glare, -- said of a flame; hence,
      of the color of burning brimstone, betokening the presence
      of ghosts or devils; as, the candle burns blue; the air
      was blue with oaths.
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   3. Low in spirits; melancholy; as, to feel blue.
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   4. Suited to produce low spirits; gloomy in prospect; as,
      thongs looked blue. [Colloq.]
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   5. Severe or over strict in morals; gloom; as, blue and sour
      religionists; suiting one who is over strict in morals;
      inculcating an impracticable, severe, or gloomy mortality;
      as, blue laws.
      [1913 Webster]

   6. Literary; -- applied to women; -- an abbreviation of
      bluestocking. [Colloq.]
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            The ladies were very blue and well informed.
                                                  --Thackeray.
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   Blue asbestus. See Crocidolite.

   Blue black, of, or having, a very dark blue color, almost
      black.

   Blue blood. See under Blood.

   Blue buck (Zool.), a small South African antelope
      (Cephalophus pygm[ae]us); also applied to a larger
      species ([AE]goceras leucoph[ae]us); the blaubok.

   Blue cod (Zool.), the buffalo cod.

   Blue crab (Zool.), the common edible crab of the Atlantic
      coast of the United States (Callinectes hastatus).

   Blue curls (Bot.), a common plant (Trichostema
      dichotomum), resembling pennyroyal, and hence called also
      bastard pennyroyal.

   Blue devils, apparitions supposed to be seen by persons
      suffering with delirium tremens; hence, very low
      spirits. "Can Gumbo shut the hall door upon blue devils,
      or lay them all in a red sea of claret?" --Thackeray.

   Blue gage. See under Gage, a plum.

   Blue gum, an Australian myrtaceous tree (Eucalyptus
      globulus), of the loftiest proportions, now cultivated in
      tropical and warm temperate regions for its timber, and as
      a protection against malaria. The essential oil is
      beginning to be used in medicine. The timber is very
      useful. See Eucalyptus.

   Blue jack, Blue stone, blue vitriol; sulphate of copper.


   Blue jacket, a man-of war's man; a sailor wearing a naval
      uniform.

   Blue jaundice. See under Jaundice.

   Blue laws, a name first used in the eighteenth century to
      describe certain supposititious laws of extreme rigor
      reported to have been enacted in New Haven; hence, any
      puritanical laws. [U. S.]

   Blue light, a composition which burns with a brilliant blue
      flame; -- used in pyrotechnics and as a night signal at
      sea, and in military operations.

   Blue mantle (Her.), one of the four pursuivants of the
      English college of arms; -- so called from the color of
      his official robes.

   Blue mass, a preparation of mercury from which is formed
      the blue pill. --McElrath.

   Blue mold or Blue mould, the blue fungus (Aspergillus
      glaucus) which grows on cheese. --Brande & C.

   Blue Monday,
      (a) a Monday following a Sunday of dissipation, or itself
          given to dissipation (as the Monday before Lent).
      (b) a Monday considered as depressing because it is a
          workday in contrast to the relaxation of the weekend.


   Blue ointment (Med.), mercurial ointment.

   Blue Peter (British Marine), a blue flag with a white
      square in the center, used as a signal for sailing, to
      recall boats, etc. It is a corruption of blue repeater,
      one of the British signal flags.

   Blue pill. (Med.)
      (a) A pill of prepared mercury, used as an aperient, etc.
      (b) Blue mass.

   Blue ribbon.
      (a) The ribbon worn by members of the order of the Garter;
          -- hence, a member of that order.
      (b) Anything the attainment of which is an object of great
          ambition; a distinction; a prize. "These
          [scholarships] were the --blue ribbon of the college."
          --Farrar.
      (c) The distinctive badge of certain temperance or total
          abstinence organizations, as of the --Blue ribbon
          Army.

   Blue ruin, utter ruin; also, gin. [Eng. Slang] --Carlyle.

   Blue spar (Min.), azure spar; lazulite. See Lazulite.

   Blue thrush (Zool.), a European and Asiatic thrush
      (Petrocossyphus cyaneas).

   Blue verditer. See Verditer.

   Blue vitriol (Chem.), sulphate of copper, a violet blue
      crystallized salt, used in electric batteries, calico
      printing, etc.

   Blue water, the open ocean.

   Big Blue, the International Business Machines corporation.
      [Wall Street slang.] PJC

   To look blue, to look disheartened or dejected.

   True blue, genuine and thorough; not modified, nor mixed;
      not spurious; specifically, of uncompromising
      Presbyterianism, blue being the color adopted by the
      Covenanters.
      [1913 Webster]

            For his religion . . .
            'T was Presbyterian, true blue.       --Hudibras.
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WordNet (r) 3.0 (2006):

Big Blue
    n 1: a reliable and deadly 15,000-pound fragmentation bomb that
         explodes just above ground with a large radius; the largest
         conventional bomb in existence; used in Afghanistan [syn:
         Big Blue, BLU-82]

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

International Business Machines
big blue
IBM

    (IBM) The best known American computer manufacturer,
   founded by Thomas J. Watson (born 1874-02-17), known as "Big
   Blue" after the colour of its logo.  IBM makes everything from
   mainframes to personal computers (PCs) and has been
   immensely successful in selling them, chiefly to business.  It
   has often been said that "Nobody has ever been sacked for
   buying IBM".

   The IBM PC in its various versions has been so successful
   that unqualified reference to a "PC" almost certainly means a
   PC from IBM, or one of the many brands of clone produced by
   other manufacturers to cash in on IBM's original success.

   Alternative expansions of "IBM" such as Inferior But
   Marketable; It's Better Manually; Insidious Black Magic; It's
   Been Malfunctioning; Incontinent Bowel Movement, illustrate
   the considerable antipathy most hackers have long felt toward
   the "industry leader" (see fear and loathing).

   Quarterly sales $15351M, profits $689M (Aug 1994).

   (http://ibm.com/).

   (1999-04-07)