The Collaborative International Dictionary of English v.0.48:

Tone \Tone\, v. t. [imp. & p. p. Toned; p. pr. & vb. n.
   Toning.]
   1. To utter with an affected tone.
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   2. To give tone, or a particular tone, to; to tune. See
      Tune, v. t.
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   3. (Photog.) To bring, as a print, to a certain required
      shade of color, as by chemical treatment.
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   To tone down.
      (a) To cause to give lower tone or sound; to give a lower
          tone to.
      (b) (Paint.) To modify, as color, by making it less
          brilliant or less crude; to modify, as a composition
          of color, by making it more harmonius.
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                Its thousand hues toned down harmoniusly. --C.
                                                  Kingsley.
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      (c) Fig.: To moderate or relax; to diminish or weaken the
          striking characteristics of; to soften.
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                The best method for the purpose in hand was to
                employ some one of a character and position
                suited to get possession of their confidence,
                and then use it to tone down their religious
                strictures.                       --Palfrey.
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   To tone up, to cause to give a higher tone or sound; to
      give a higher tone to; to make more intense; to heighten;
      to strengthen.
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