To obtain a composition having excellent dyeing properties and rheological properties by treating a crude organic pigment with a pigment derivative having a heteroaryl(thio)amidomethyl substituent bonded to the carbonyl functional group of each (thio)amidomethyl bonding group through the ring nitrogen atom of the heteroaromatic group.

A suitable example of the heteroarylamidomethyl and/or heteroarylthioamidemethyl pigment derivatives (hereinbelow referred simply to as a pigment derivative) is a compound of the formula (wherein Q is an organic pigment part; X is O or S; Het is a heteroaromatic group bonded to the carbonyl or thiocarbonyl functional group of a (thio)amidomethyl bonding group through its ring carbon atom; and is 1-4(desirably 1). The organic pigment is mixed with the pigment derivative in a strong mineral acid, is wet- or dry- mixed with the pigment derivative or the pigment derivative is added to the system of synthesizing the pigment or treated in the presence of the pigment derivative. A desired pigment composition can be prepared by any of these methods.