Some Pigment Left Behind After Mole Biopsy

If a shave biopsy was performed on the mole, there is a chance for the mole to grow back.  I would not be too concerned with the pigment returning.  I would still have the mole evaluated by your doctor.  

If a mole was shaved and read as benign then I would not worry about recurrent pigment. If the pigmentation bothers you it can be further removed or can often be faded with cryotherapty(freezing). 

The goal of a biopsy is to determine if something that looked atypical to the eye during your exam, is in fact atypical -- cancerous or pre-cancerous.  If the pathology report shows a benign process, removal of the residual pigment is not necessary.  Many moles have some residual pigment, or pigment recurs, after a shave biopsy.  If the color begins to change or returning pigment continues to grow or change, then I would have it re-examined and probably excised.  Make sure your moles are evaluated and treated by a Board Certified Dermatologist, and that all pigmented lesion biopsies are read by a Board Certified in Dermatopathologist.