Lewis & Short

vĭŏlācĕus, a, um, adj. [viola, II.], violet-colored, violet: purpura, Nep. ap. Plin. 9, 39, 63, § 136: flos herbae, Plin. 22, 18, 21, § 47: gemma, id. 37, 10, 61, § 170.