If it's too dark/blue, I've been told leaving it in sunlight for a while is helpful. And in my experience having had blue streaks of dye in my hair before (first thing I did when I came to college, I had a job before that where I couldn't dye my hair) is that it fades to green anyway.

CAN'T WAIT UNTIL IT GETS HERE.

And I think I have enough remnants now to scarfalicious up my Terra costume. XD