Michigan,
According to the CRC Handbook the green color is the result of the chromium reacting with the water in the wood and resulting in Cr2O3, chromium sesquioxide. This compound is reported to be soluble in alkalai solutions. You might want to try stripping the stock and then cleaning it with lye. That might leach out the chromium oxides enough to diminish the green color chromium usually ends up imparting. It might save you from scraping or sanding off the wood that has absorbed the stain. Since chromic acid is a water-based stain, there might be some locations where it has penetrated quit deeply into the wood. In that regard it behaves similar to iron nitrate or iron acetate (vinegaroon). However, the iron compounds are color-fast and reliable!
"Magic Maple" stain is chromic acid. Chromium oxide, CrO3, reacts with water to yield chromic acid. Given enough time anything stained with that product will start turning green as the chromate radical reacts with the moisture in the wood. In my view there is absolutely no justification for using chromic acid on wood when there are so many other stains out there that are reliable, easy to use and non-toxic.
And as a side note, ALL chromium compounds are potentially toxic. Every chromium atom in the universe has the ability to become "hexavalent chromium". Indeed, the chromium in chromium tri-oxide, CrO3, has a valence of six!
Best Regards,
JMC
John Cholin