i used to die my hair brown, but i left it on too long once and it went practically black. so i used a prelightner, its not a blonde hair dye, you leave it on and it basically strips the hair of its colour. its pretty risky cause it could turn your hair a strange orange colour. but i left it on until i could visibly see that it wasnt black any more and then i washed it off. i reckon you could use the prelightner so that its not jet back any more and then use a dark brown hair dye. hopefully cause you still want a dark hair colour it should work out ok. good luck! : )