A method for coloring or bleaching a hair comprising steps of: (a) applying a first formulation comprising a hair coloring agent or bleaching agent to the hair; and (b) applying to the hair a second formulation comprising a hair composition represented by one or both of the following formulas: wherein - R 1 - R 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen, and R 5 and R 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, an alkylaryl group or a heterocyclic group; and - R' 1 - R' 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen; and R' 5 and R' 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, or a heterocyclic group, excluding R' 5 and R' 6 being simultaneous hydrogens, wherein the aliphatic hydrocarbon group, the alicyclic hydrocarbon group, the aryl group, the alkylaryl group or the heterocyclic group is substituted with at least one hydroxyl group; and wherein the steps (a) and (b) are performed simultaneously. (a) applying a first formulation comprising a hair coloring agent or bleaching agent to the hair; and (b) applying to the hair a second formulation comprising a hair composition represented by one or both of the following formulas: wherein - R 1 - R 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen, and R 5 and R 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, an alkylaryl group or a heterocyclic group; and - R' 1 - R' 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen; and R' 5 and R' 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, or a heterocyclic group, excluding R' 5 and R' 6 being simultaneous hydrogens, wherein the aliphatic hydrocarbon group, the alicyclic hydrocarbon group, the aryl group, the alkylaryl group or the heterocyclic group is substituted with at least one hydroxyl group; and wherein the steps (a) and (b) are performed simultaneously. - R 1 - R 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen, and R 5 and R 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, an alkylaryl group or a heterocyclic group; and - R' 1 - R' 4 are independently hydrogen, a hydrocarbon radical having 1 to 10 carbon atoms, a hydroxyl group, an amino group, a sulfhydryl group, an aryl group, or a halogen; and R' 5 and R' 6 are independently hydrogen, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group, or a heterocyclic group, excluding R' 5 and R' 6 being simultaneous hydrogens, <EOS>