Bicyclic 5-5 heteroaromatic compounds having a ring junction nitrogen and incorporating thia or oxa heteroatoms heteroatoms. Compositions for the oxidative dyeing of keratin fibers, comprising a medium suitable for dyeing and one or more bicyclic 5-5 heteroaromatic compounds having a ring junction nitrogen and incorporating thia or oxa heteroatoms heteroatoms. A method for oxidative dyeing of keratin fibers, comprising applying such compositions in the presence of an oxidizing agent, for a period sufficient to develop the desired coloration.