The Collaborative International Dictionary of English v.0.48:

Impurple \Im*pur"ple\, v. t. [imp. & p. p. Impurpled; p. pr. &
   vb. n. Impurpling.] [Pref. im- in + purple. Cf.
   Empurple.]
   To color or tinge with purple; to make red or reddish; to
   purple; as, a field impurpled with blood.
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         Impurpled with celestial roses, smiled.  --Milton.
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         The silken fleece impurpled for the loom. --Pope.
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