A process for preparing colorants of the general formula (Ia), (Ib) or (Ic) or mixtures thereof, comprises reacting (a) tetracarboxylic acids or their functional derivatives with (b) at least one compound selected from i. aliphatic amines, ii. aromatic amines, iii. aliphatic diamines, iv. aromatic diamines, (c) optionally in the presence of further additives, (d) optionally in the presence of wetting agents in a mixing apparatus. These colorants are useful for coloration of macromolecular organic and inorganic materials of natural and synthetic origin.