Toners can take bright yellow or golden hair to a more natural-looking dusty, ashy, or platinum blonde. And they can be a lifesaver if your bleach job has gone horribly wrong and you're now walking around with a brassy orange mane.
What kind of toner cancels out yellow?
Blue based colors and toners are good at killing yellow and they should be your first choice in such situations. Use Ugly Duckling's blue based ash blonde colors (anything ending in "1b"). Blue cancels out yellow on the color wheel.