The invention relates to the use of compounds corresponding to formula (I) ##STR1## in which one of the substituents R.sup.1 or R.sup.2 is a nitro group while the other is hydrogen, halogen, an amino group, a mono- or dialkylamino group containing C.sub.1-4 alkyl groups, a C.sub.1-4 alkyl or alkoxy group, R.sup.3 and R.sup.4 independently of one another represent hydrogen or a C.sub.1-4 alkyl group, A is a >CHR.sup.6 - or a >C.dbd.O- group, where R.sup.6 is hydrogen or a C.sub.1-4 alkyl group, and R.sup.5 is hydrogen or a C.sub.1-4 alkyl group, or salts thereof as substantive dyes in hair-dyeing compositions.When the substituent groups in formula I represent one of the combinations I-IV shown in the table below, the compounds are novel and are useful in hair-dyeing compositions.______________________________________ R.sup.1 R.sup.2 R.sup.3 R.sup.4 R.sup.5 A ______________________________________ I: H NO.sub.2 H CH.sub.3 H CH.sub.2 II: H NO.sub.2 CH.sub.3 CH.sub.3 H CH.sub.2 III: NH.sub.2 NO.sub.2 H H H CH.sub.2 IV: H NO.sub.2 H H CH.sub.3 CH.sub.2. ______________________________________