黒痣[kuroaza] black mole
青痣[aoaza] bruise

赤痣[akaaza] red birthmark (esp. a hemangioma)

お歯黒[ohaguro] tooth blackening
暗黒期[ankokuki] eclipse period
暗黒時代[ankokujidai] Dark Ages
暗黒大陸[ankokutairiku] Dark Continent (i.e. Africa)
黒い[kuroi] black

黒い霧[kuroikiri] thick fog
黒くする[kurokusuru] to blacken
黒ずむ[kurozumu] to blacken
黒っぽい[kuroppoi] dark