Stained temporary veneers (Photo)

You probably should go back to your dentist to remove the coloration. Veneer temps are more porous than the porcelain will be and will pick up that kind of stain. Your dentist may need to remove some of the outer layer of plastic to remove the stain. If you can't get in to see him/ her, maybe if you tried a whitening kit, that might help. Walgreens sells them. I hope this helps!

I agree, try to get your dentist to abrade off the stain. If that doesn't work, depending on how long you have until your final veneers are bonded, you might consider paying to have the temps replaced.

The only way to get rid of the color is to remake the temps. I have had this happen to several patients and it always involves tumeric tea or yellow curry. 

There really is no treatment that can do what you want.  Remaking the veneers is the only solution, but your case may be ready or soon ready to seat.  Call your dentist and see the status of your permanent veneers.