How do you remove a dark water stain from a "blonde" hard wood floor?

I don't know how old the stain is and cannot find anyting specifically for 'blondes' but for hardwood floors in general I did find a few links thant might be of help to you and have posted them below. I do hope they are of some help with this dilemma. Good Luck and thanks for using Hometalk for help.

http://www.ehow.com/how_4968149_remove-water-stains-hardwood-floors.html#page=9

http://www.ehow.com/how_5850082_remove-water-spots-wood-floors.html

I've always used wood bleach, after removing the finish, or mixed household bleach and water. I like to do multiple light applications so it doesn't get too light.

I've also read you can soak a cotton cloth in hydrogen peroxide and place it on the stain until it lightens up enough, then use rag to wipe up any excess.

If you get it too light just apply a bit of stain and then spar varnish when dry.

https://www.cleanmama.net/2012/07/how-to-wash-hardwood-floors-with.html

Mayonnaise Apply a dab with a soft cloth and rub it into the mark in a circular motion. ...