try Mr. Eraser
try some rubbing alcohol, if that does not work some Carbon Tetrachloride would, but that stuff is pretty toxic.
YEP, Rubbing alcohol...if it's pourous tiles...you may have already rubbed it into the tile with the other chemical but rubbing alcohol is always my first stop for ink...
Rubbing alcolhol is the best choice. It took it out my carpet when my brother sat on it with a pen in his pocket :P It even removes permanent marker from a white board.
Goof off. Sold at big box stores. works on lots of things.