The present invention relates to a process for treating keratin fibers, especially human keratin fibers such as the hair, using i) at least one triarylmethane or sulfonophthalein direct dye of formula (I) or (I′) as defined below, ii) an alkaline revealer, iii) an eraser at acidic pH. A subject of the invention is also a composition comprising at least one triarylmethane direct dye of formula (I) or (I′) as defined below and at least one thickener and/or at least one hydrotropic solvent, and a multi-compartment kit comprising i), ii) and iii) in three separate compartments. The present invention makes it possible in particular to obtain keratin fiber coloring with intense and persistent tints which can be modified, erased and reformed several times without any loss of color.