We used a DuPont product on our granite for stains. Worked very well. It was like a paste that you put on it and it sucked stains from the pores of the stone.
Google that and you should find it. Got on Amazon.
Make a slurry out of baking soda & hydrogen peroxide and cover the stain and let sit over night. (test in an inconspicuous place first to make sure it doesn't stain/discolor)