I dyed my blonde hair with a semi-permanent black dye about 5 weeks ago, it has turned my hair green and I need to get it out within 3 days.

Is this possible? Can anyone point me in the right direction? I really need to get it back to its original colour.

Applying a brown or black color over blonde hair may result in a green cast. To go from blonde to dark, it requires a 2 step coloring process.

In order to go back to your to your original color, the black dye has to be stripped from your hair. After the dye is removed, you may apply your desired color. You can use a hair color remove to strip the unwanted color.