Yellow and Blue Make Green! (Hair Issue)

[Disneyphile]

Um... Wendybeth???

How can I get blue hair dye to actually look blue and not green?

I bleached first, and it was a light golden blonde, but it gave the blue a very prominent greenish undertone.

Do I need to bleach completely white first?

Or, should I just add another round of blue and let it set for longer?

Besides this, I'm very happy with the new dye job. Once I get the streak to a proper blue, it'll be perfect.