Hair dye composition

A hair dye composition comprising an azo dye represented by any one of the following formulas (1) to (5):

• wherein, R1 represents a hydrogen atom or a substituent and A represents a monocyclic or bicyclic, aromatic heterocyclic residue which may have a substituent and has a free valence at a carbon atom of the residue, with the proviso that R1 and A each contains, in the structure thereof, none of a carboxy group, a sulfo group and a quaternary ammonium group,
• wherein, R2a and R2b each represents a hydrogen atom or a substituent, and A′ represents a monocyclic or bicyclic, aromatic heterocyclic residue which may have a substituent and has a free valence at a carbon atom of the residue, with the proviso that R2a, R2b, and A′ each contains, in the structure thereof, none of a carboxy group, a sulfo group, and a quaternary ammonium group,
• wherein, R2a, R2b, and A′ have the same meanings as defined above,
• wherein, R represents a coupler component, X1, X2, X3, and X4 represent atoms which are coupled together with the carbon atom sandwiched between X1 and X4 to form a 5-membered heteroaromatic ring, V1 and V2 each represents a substituent, and a1 and a2 each stands for an integer from 0 to 3, and
• wherein, R3 represents a hydroxy group, an alkylsulfonylamino group, an arylsulfonylamino group, or —CH(R4)(R5) (R4 and R5 each representing a substituent having a Hammett's constant σ of 0.2 or greater and less than 1.4), W represents a sulfur atom or N—R6 (R6 representing a substituent), X, Y and Z each represents a nitrogen atom or a carbon atom, with the proviso that at least one of X, Y and Z is a nitrogen atom and when Z represents a nitrogen atom, either one or both of X and Y represent a nitrogen atom, R7 and R8 each represents a substituent, and b stands for from 0 to 2, with the proviso that when b stands for 2, two R8s may be coupled to form an aromatic ring or a heteroaromatic ring.