The present invention relates to a composition for dyeing human keratin fibers, comprising at least one natural dye, at least one triarylmethane synthetic direct dye and at least one compound of formula (I), in which Y represents a C1-C4 hydroxyalkyl group or a C1-C4 hydroxyalkyloxy radical, n denotes an integer ranging from 0 to 5, and X, which may be identical or different, represents a C1-C4 alkyl radical or a halogen. The invention also relates to a process for dyeing human keratin fibers using this composition.