Keratin dyeing compounds, keratin dyeing compositions containing them, and use thereof

A keratin dyeing composition comprising:

• (A) a medium suitable for dyeing;
• and
• (B) one or more tricyclic 5-6-5 heteroaromatic keratin dyeing compounds having two heteroatoms selected from an unsubstituted or substituted member of the group consisting of benzo[1,2-b;4,5-b′]difuran, 5H-1-oxa-5-aza-s-indacene, 1-oxa-5-thia-s-indacene, 1,5-dihydro-pyrrolo[2,3-f]indole, 5H-1-thia-5-aza-s-indacene, 1,5-dithia-s-indacene, benzo[1,2-b;5,4-b′]difuran, 7H-1-oxa-7-aza-s-indacene, 1-oxa-7-thia-s-indacene, 1,7-dithia-s-indacene 1,7-dihydro-pyrrolo[3,2-f]indole, 7H-1-thia-7-aza-s-indacene, benzo[2,1-b;3,4-b′]difuran, 8H-1-oxa-8-aza-as-indacene, 1-oxa-8-thia-as-indacene, 1,8-dihydro-1,8-diaza-as-indacene, 8H-1-thia-8-aza-as-indacene, 1,8-dithia-as-indacene, benzo[1,2-b;4,3-b′]difuran, 6H-3-oxa-6-aza-as-indacene, 3oxa-6-thia-as-indacene, 3,6-dihydro-3,6-diaza-as-indance, 6H-3-thia-6-aza-as-indacene, and 3,6-dithia-as-indacene.