Dispersants for organic pigments

1 2 3 4 A dispersant for an organic pigment contains a compound represented by the following formula (1): wherein Rand Rmay be the same or different and each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a primary, secondary or tertiary amino group, an alkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted phthalimidomethyl group, Rand Rmay be the same or different and each independently represents a hydrogen atom or a lower alkyl group, and n means an average number of introduced sulfonic groups and stands for a number of from 0.5 to 3; or at least one salt selected from the group consisting of its metal salt, ammonium salt, organic amine salt, and organic quaternary ammonium salt. Also disclosed are a readily-dispersing pigment composition, a pigment dispersion, a colored coating fluid for color filters, a fabrication process of a color filter and a color filter, all of which make use of the dispersant.