The wood becomes like that because of moisture, so if you are using wood/homogeneous tiles do use a tile sealer
You can seal your tiles by using something called HCL89.
I usually get it from http://hcl89.byethost10.com or http://hcl89.atwebpages.com
What it does is that it removes any stains as well as polishes your tiles and seals it. The tile sealer is important because it prevents moisture from damaging your tiles in the long run
Hope this helps you out