i have had a tank/stand on my red oak hardwood floors for more than 4 years with no issues. the stand was directly sitting on the floor with a couple pieces of felt in the corners, as that allowed me to slide the tank when the water level was low.
i never had an issue with water, as any spills i keep a towel on the floor when i'm playing in the tank, and just cleaned up any drips/spills immediately.
as for discoloration, it wood depend on what type wood it how would age. if the tank would be on a floor such as red oak or natural cherry, and would be in a place that gets natural sunlight and the stand is now blocking that, you would have a lighter section of flooring once you moved the tank. florescent lighting tends not to age the floor (at least not nearly to the same degree as natural sunlight).
hth