Sodium metabisulfite is an decent bleach neutralizer. 1/2 teaspoon of sodium metabisulfite added to 1 gallon of water will effectively neutralize chlorine bleach residue.
Sodium Thiosulfate is more often sold within this industry for this specific purpose, as it has far less odor. But sodium metabisulfite is more readily obtainable, as you probably are already using it as a reducer/tannin stain remover.