by Omega2064
Whooo! Success! Sunlight was the catalyst.The first try just sitting around in the house didnt work. So I set it out at noon as it was nice and sunny out and 4 hours later the tile looks fine.
The tile in the middle originally looked like the greenish tiles to the left.
All this took was immersing the tile in hydrogen peroxide and leaving it out in the sun for 4-6 hours.
Hope that helps anyone with that particular problem.