The invention relates to a composition A which is preferably compact and/or anhydrous comprising at least 20% of powder of indigo yielding plant(s) and at least one oil and/or one butter and also to an aqueous composition B preferably in the form of a poultice for dyeing keratin fibres to the process for dyeing keratin fibres by treating said fibres with said composition and to the use of the composition and of a poultice for dyeing keratin fibres. Compositions A and B according to the invention make it possible to dye keratin fibres with strong and chromatic dyeing results that are resistant to washing perspiration sebum and light and that are moreover long lasting without impairing said fibres. Furthermore the use of compositions A and B does not give off any raw material dust (dust free). These compositions are easy to use in total safety and with no risk of staining. In addition composition A and the dyeing active agent remain stable on storage. The treated keratin fibres have a very pleasant aesthetic appearance and their integrity is respected.
