Aqueous-based hair dyeing composition containing a soluble bismuth salt complex and a reducing compound

In a hair dyeing composition comprising a metal salt and a sulfur-containing reducing compound in an aqueous vehicle, the improvement wherein said metal salt comprises a water-soluble complex of a bismuth salt of an alpha-hydroxy, polycarboxylic acid amounting up to about 5% by total weight of the composition, with a nitrogen-containing complexing agent selected from the group consisting of ammonia and triethanolamine amounting to from 50 to about 400 moles per mole of bismuth, said reducing compound amounting to from about 0.5 to 10 moles per mole of bismuth.