From The Collaborative International Dictionary of English v.0.48 [gcide]: Empurple \Em*pur"ple\, v. t. [imp. & p. p. Empurpled; p. pr. & vb. n. Empurpling.] [Pref. em- + purple. Cf. Impurple.] To tinge or dye of a purple color; to color with purple; to impurple. "The deep empurpled ran." --Philips. [1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
empurple
v 1: color purple [syn: purple, empurple, purpurate]