Styryl hydroxy(cyclo)alkylamino thiol/disulfide compounds (I) and their organic or inorganic acid salts, optical isomers, geometrical isomers or solvates such as hydrates, useful as fluorescent dye, are new. Styryl hydroxy(cyclo)alkylamino thiol/disulfide compounds of formula (I) and their organic or inorganic acid salts, optical isomers, geometrical isomers or solvates such as hydrates, useful as fluorescent dye, are new. Either R 1 : 1-6C alkyl substituted by one or more OH groups and R 2 : 1-6C alkyl optionally substituted by one or more OH groups or NR 1R 2 : saturated heterocyclic radical substituted by OH, (poly)hydroxy(1-4C)alkyl or -C(O)OR1a R1a : H, 1-4C alkyl or -C(O)-O ->(in which anionic counter ion (An ->) is absent) R 3 : N or -C(O)OR1b R1b : H, alkaline metal, 1-6C alkyl or -C(O)-O ->(in which anionic counter ion (An ->) is absent) Z : -C(O)-N(R)-, -N(R)-C(O)- or 1-10C divalent alkylene interrupted by amido group -C(O)-N(R)- or -N(R)-C(O)- n : 1 or 2 m : 0 or 1 An -> : anionic counter ion Y 1 : H, alkaline metal (both preferred), alkaline-earth metal, ammonium group (N +>Ralpha Rbeta Rgamma Rdelta ), phosphonium group (p +>Ralpha Rbeta Rgamma Rdelta ) or thiol protecting group and Ralpha , Rbeta , Rgamma , Rdelta : H or 1-4C alkyl. Provided that when: n and m are 1, then Y 1is H or protecting group of thiol function and n is 2, then m is 0 and (I) contains other cations, it is associated to one or more counter anionic ion to achieve the electroneutrality of (I). Where the bond between the pyridinium cycle and the double bond of the styryl group is positioned in 2 or 4 position of pyridinium. Independent claims are included for: (1) a coloring composition comprising (I), in a medium (2) a method for coloring keratin materials comprising applying the composition on the keratin materials optionally in the presence of reducing agent and (3) a device with several compartments comprising a first compartment comprising a coloring composition comprising (I) a
