TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The heterocyclic compound is dispersed in the medium, and is preferably of formula (1a).Y'=atomic group required to form 4-7 membered ring (Q) represented by formulae (2-7) or their tautomer;R21,R22,R31,R32,R34,R41,R44,R51,R52,R62,R64,R73-R75=H or monovalent substituent, and at least one of R21, R31,R51, R52 and R41 is oxygen atom;R23-R25,R33,R35,R43,R45,R53,R54,R63=optionally substituted heteroatom, and at least one of R24 and R25, R53 and R54 and R24 and R35 and R45 is oxygen atom;andZ71,Z72=-N= or -C(R75).When R24 has substituent, the substituent is optionally coupled with R22 to form a ring. When R25 has substituent, the substituent is optionally coupled with R21 to form a ring. When R33 has substituent, the substituent is optionally coupled with R31 to form a ring. When R35 has substituent, the substituent is optionally coupled with R31 to form a ring. When R43 and/or R45 have substituent, the substituent is optionally coupled with R41 to form a ring. When R53 has substituent, the substituent is optionally coupled with R52 to form a ring. When R54 has substituent, the substituent is optionally coupled with R51 to form a ring. When R63 has substituent, the substituent is optionally coupled with R62 to form a ring. Preferred Definitions:    X1,X2=sulfur atom;and    R=nitrogen-containing 6-membered ring.    SPECIFIC COMPOUNDS - 290 Heterocyclic compounds, such as 2-(1,3)dithiolo(4,5-b)pyrazin-2-ylidenecyclopentanone of formula (1), 5-(1,3)dithiolo(4,5-b)pyrazin-2-ylidenecyclopent-2-en-1-one, 2-(1,3)dithiolo(4,5-b)pyrazin-2-ylidenecyclopent-4-ene-1,3-dione, 2-(1,3)dithiolo(4,5-b)pyrazin-2-ylidenecyclohexanone and 2-(1,3)dithiolo(4,5-b)pyrazin-2-ylidenecyclohexane-1,3-dione are disclosed.    EXAMPLE - 5-Methyl-2-phenyl-3-pyrazolone (in g) (6.43) was dissolved in N,N-dimethyl acetamide (20 ml). Triethylamine (10.3 ml) was added under nitrogen atmosphere, and carbon disulfide (2.23 ml) was added. The resulting solution was stirred at room temperature for 1 hour. 2,3-Dichloropyrazine (5) was added and stirred under nitrogen atmosphere to produce heterocyclic compound at yield of 11%. The obtained compound was mixed with mixture of N,N-dimethylacetamide and water, and stirred. The resulting product was filtered and dried. The obtained solid (0.25), sodium oleate (0.05), glycerine (0.5) and deionized water (4.2) were mixed and pulverized to produce coloring dispersion composition. The composition had excellent light resistance.