Lewis & Short

ferrūgo, ĭnis, f. [ferrum; like aerugo from aes], iron-rust (syn.: aerugo, rubigo).

  1. I. Prop., Plin. 23, 8, 79, § 151.
    1. B. Transf., the color of iron-rust, a darkred, dark-chestnut, a dusky color: nuclei vestiti aliā ferruginis tunicā, Plin. 15, 10, 9, § 35; also sea-green: viridis ferrugine barba, Ov. M. 13, 960: excutit obscurā tinctas ferrugine habenas, id. ib. 5, 404; 15, 789: sol caput obscurā nitidum ferrugine texit, gloom, Verg. G. 1, 467: maesta obtenta Ditis ferrugine regna, id. Cul. 273: pectus manu ferrugine tincta Tangit, Ov. M. 2, 798: pictus acu chlamydem et ferrugine clarus Hiberā, purple, Verg. A. 9, 582; cf.: peregrinā ferrugine clarus et ostro, id. ib. 11, 772: violas ferrugine pingit, Claud. Rapt. Pros. 2, 93.
  2. * II. Trop., envy (cf. aerugo): animusque mala ferrugine purus, Auct. Pan. ad Pis. 95.