Bleach perhaps? Try it of a scrap bit of tile first!

You can get paultice type material that sucks the stain out of marble, not sure how well it would work on pen. I always use a kiddies felttip pen on tile as it wipes off easily, just use the permanent type when wet cutting, masking tape then mark out if its stone.

Mudster may be along with a word od wisdom.

Jason

Brake fluid