Lewis & Short

purpŭrissum, i, n.

    (
  1. I. masc. collat. form purpŭrissus, Hier. Ep. 54, 7), = πορφυρίζον, a kind of dark purple color, used for dyeing red and as a cosmetic, Plin. 35, 6, 12, § 30; Plaut. Most. 1, 3, 104; Naev. and Afran. ap. Non. 218, 30 and 31; Hier. Ep. 127, 3.
  2. II. Transf.: quid in oratione meā purpurisso litum, highly colored, Front. Or. 2, p. 248.