*euchroic*

a. [ Gr. &unr_; well-colored; e'y^ well + &unr_; color. ] (Chem.) Having a fine color. [ 1913 Webster ]

Euchroic acid (Chem.), an organic, imide acid, obtained as a colorless crystalline substance, C12H4N2O8 by heating an ammonium salt of mellitic acid. By reduction it is changed to a dark blue substance (euchrone), -- hence its name. [ 1913 Webster ]