The Collaborative International Dictionary of English v.0.48:

vivid \viv"id\ (v[i^]v"[i^]d), a. [L. vividus, from vivere to
   life; akin to vivus living. See Quick, a., and cf.
   Revive, Viand, Victuals, Vital.]
   1. True to the life; exhibiting the appearance of life or
      freshness; animated; spirited; bright; strong; intense;
      as, vivid colors.
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            In dazzling streaks the vivid lightnings play.
                                                  --Cowper.
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            Arts which present, with all the vivid charms of
            painting, the human face and human form divine.
                                                  --Bp. Hobart.
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   2. Forming brilliant images, or painting in lively colors;
      lively; sprightly; as, a vivid imagination.
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            Body is a fit workhouse for sprightly, vivid
            faculties to exercise . . . themselves in. --South.
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   Syn: Clear; lucid; bright; strong; striking; lively; quick;
        sprightly; active.
        [1913 Webster] -- viv"id*ly, adv. -- viv"id*ness, n.
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WordNet (r) 3.0 (2006):

vividness
    n 1: interest and variety and intensity; "the Puritan Period was
         lacking in color"; "the characters were delineated with
         exceptional vividness" [syn: color, colour,
         vividness]
    2: chromatic purity: freedom from dilution with white and hence
       vivid in hue [syn: saturation, chroma, intensity,
       vividness]