Method for dyeing keratinous fibres using an aminoindole in combination with a quinone derivative

A process for dyeing keratinous fibers comprising applying to said fibers at least one composition A comprising in a medium suitable for dyeing said fibers at least one aminoindole having the formula ##STR7## wherein R.sub.1 represents hydrogen or a linear or branched C.sub.1 -C.sub.4 alkyl,

• R.sub.2 and R.sub.3 represent hydrogen, C.sub.1 -C.sub.4 alkyl, carboxyl or (C.sub.1 -C.sub.4) alkoxycarbonyl,
• R.sub.4 represents hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 hydroxyalkyl, C.sub.2 -C.sub.4 polyhydroxyalkyl, acetyl or C.sub.1 -C.sub.6 aminoalkyl wherein the amine moiety optionally in monosubstituted or disubstituted by a C.sub.1 -C.sub.4 alkyl,
• Z.sub.1 and Z.sub.2, each independently, represent hydrogen, C.sub.1 -C.sub.4 alkyl, halogen or C.sub.1 -C.sub.4 alkoxy,
• NHR.sub.4 occupying the 4, 5, 6, or 7 positions;
• and
• a salt of said aminoindole, the application of said composition A to said fibers being preceded or followed by the application to said fibers of composition B comprising, in a medium suitable for dyeing said fibers at least one quinone derivative selected from the group consisting of an orthoquinone, a para-benzoquinone, an orthobenzoquinone monoimine, an orthobenzoquinone diimine, a para-benzoquinone monoimine, a para-benzoquinone diimine, a 1,2-napththoquinone, a 1,4- naphthoquinone, an ortho benzoquinone sulphonimide, a para-benzoquinone sulphonamide, an .alpha.,.omega.-alkylene-bis-1,4-benzoquinone, a 1,2-naphthoquinone monoimine, a 1,2-napthoquinone diimine, a 1,4-naphthoquinone monomine and a 1,4-napthoquinone diimine,
• the said amino indole and said quinone derivative being chosen such that the difference in the redox potential E.sub.i of said amino indole, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the redox potential E.sub.q of said quinone derivative, determined at pH 7 in a phosphate medium by polarography on a mercury electrode relative to a saturated calomel electrode is such that .DELTA.E=E.sub.i -E.sub.q .ltoreq.470 mV.