I colred my hair from darkbrown to blonde with bleach then I put a ash blonde.. My hair turned greenish blonde.Can I use a champagne blonde to get the green to go away.. the green is very faint

Yes, I believe it will not show up xx

No. Champagne blonde has a hint of gold. Gold mixed with green will not cancel the green. You need to go to the opposite side of the color wheel my dear. Opposite green on the wheel is red. You could try a neutral blond in semi or demi permanent and see if that helps. If not try a warmer blond which will have a tad more red in the base. I hope this helps dearie :)