Hi, again, Lynn. There are several different kinds of wood stains. Some can be removed with bleach and some with oxalic acid. Some can not be removed with anything other than a very dangerous chemical combination that should only be used by professionals. Try regular bleach first. Make sure that any clear finish like varnish, lacquer or polyurethane is removed. Then pour bleach on a rag and wipe it on a small portion of one door. Watch to see if it has any effect. If it does not, then neutralize the bleach with 2 cups of vinegar in a gallon of water. If it does seem to work, do the whole piece and then neutralize with the vinegar solution.
If the bleach didn't work, mix the oxalic acid according to package directions. This should be available in home centers or specialty paint stores. I have no idea what the trade or brand name would be, but someone should recognize "oxalic acid". Put it on the piece and see if it works. If it does or does not, neutralize it with half a box of baking soda in a gallon of water. Then rinse in plain water. Hopefully, one of these two will work.
When working with any of these products, wear heavy rubber gloves, not just thin latex ones like a doctor uses. Also wear eye protection. When you mix the oxalic acid, wear a dust mask. The dust from the powder can be very irritating.
Since you have used water on wood, the grain will be raised. You will have to sand lightly with about 150 grit paper. Sanding louvers is not fun but it has to be done.
My son-in-law is from Gillingham, Kent. People from Britain would be OK if we could just teach them to spell words like louver and color correctly. LOL