I have used Wella Koleston 7/1 on my dark brown (30% grey) hair and although the greys r a lovely colour the rest has gone light brown with an odd yellow/ginger tinge. I assume I have tried to go too light for my dark hair. Is there anything I can do in the short term to make my hair ash? What is the best Wella colour to give me a nice light ash drown colour with NO yellow or warmth? I am keen not to bleach to get any lighter but do have a natural tendency to become brassy and warm.