Method of preparing a pigment composition

A method of preparing a pigment composition comprising wet or dry milling a pigment selected from the group consisting of dianthraquinone pigments, diketopyrrolopyrrole pigments and a mixture thereof, in the presence of a compound represented by Formula 1:

• where Q denotes —NH(CH2)nNR1(R2) group or hydroxyl group;
• R denotes —NH(CH2)nNR1(R2) group;
• R1 and R2 each independently denote an alkyl group having 1 to 4 carbon atoms, or R1 and R2 may form, together with the nitrogen atom to which they are bonded, a nitrogen-containing 5- or 6-membered heterocyclic ring which may contain an additional nitrogen atom or an oxygen atom in the ring;
• and n denotes an integer of 1 to 4
• wherein the wet milling is carried out by kneading a mixture comprising the pigment, the compound, a watersoluble inorganic salt and a watersoluble organic solvent which does not substantially dissolve the inorganic salt, adding the kneaded mixture to water, stirring the resultant mixture to form a slurry. and filtering and water washing the slurry to remove the inorganic salt and the organic solvent.