I have naturally brown hair that I have been dying blue black for around a year. Last month I decided to bleach my fringe blonde, which I did in two goes.
First bleached it orangey, then bleached it more to a sort of yellow. After having it blond for a months I've now decided I want it all blue black again so I dyed blue black over the blond part.
Now where it was blond the dye has faded faster than the rest of my hair and gone an odd greenish colour.
Any ideas on how to stop it doing that and/or get it dark again?

Sounds like your hair was too yellow so that's why it's going green.
Either bleach it to a more pale yellow and dye it again, or you can just dye over it again.
But it won't stop it from going green as it fades.
What dye did you use anyways?

Was the black dye an ash tone? ash tones always go greeny toned or swampy when they are used over bleached hair, or being bleached out. use a darker neutral toned dye instead. that should over it.

Over bleached hair you might try a semi/demi permanent color. Your bleached hair is very porous and the permanent color's molecules don't have much to adhere to. The semi permanent haircolor is not attempting to lift anything, only deposit color, so it should work better. I agree you should try a neutral based color.

You could also try a neutral filler (available at Sally's) if you want to use a permanent haircolor. It give those molecules something to stick to when you use the haircolor. Good luck!

I'd go for a rich dark brown colour - something with warmish tone to it will cancel out the green and prevent it from happening again. If you think your hair has been over-processed I'd go with cancankant said and use a semi.

Thanks =]

I've got another dye to dye over it again which is a natural black colour which says it's a warmer colour than the blue black was on the box. I'm going to try that and if that doesn't work, I'll try a semi permanent one.

x_Hopeless_Deviate_x, the blue black I used was Loreal Feria Blue Black Starry Night 122 (I think). The blonde bleach was Jerome Russell Bblonde high lift powder bleach and 40vol. cream peroxide.

Thanks for the help =]

Ah ha!
That's why.
I've used that exact dye myself several times over bleached hair.
It was even pale yellow, no orange tones at all.
Looked great at first but the same thing always happened when it faded.
Turned a murky colour like grey or green.
So I'm not surprised you're having the same problem.
But it sounds like you have a good plan.
Hopefully the other black dye will work better.
If not, there's always semi-permanent ones!


PS You're welcome!