coffee stain on absolute black granite

Hello,

Untill now your site was a great help,I have a nero assoluto Granite (http://tanbrown.org) Counter (http://GialloFiorito.com) top, I have no problem with it, but my sister has a problem with her Granite (http://tanbrown.org) black absolute, she has a stain on it first she thought it was oil stain, but now she realise it's a coffee stain, and (http://maplered.com) she lives in holland (http://maplered.com) . please advice??????????

How can we remove it?

Thank you,
Zizzz