2 months post Mohs on scalp I am still totally bald where I was shaved for surgery. Will it grow back? Can I use scalp dye?

Without a photo, it is very difficult to appropriately answer your question. It would also be helpful to know some of the details of the repair, your age range, and whether you have experienced any thinning of your hair prior to the surgery.

If the area was JUST shaved prior to the surgery, then that area should be able to regrow the hair just fine. However on the actual site of the Mohs itself, you could have issues with hair regrowth simply because scar tissue may have formed there which may make affect the follicles and not allow hair regrowth there. There is always a chance of this happening. Regarding the dye, it would be best to have the site examined by your dermatologist or Mohs surgeon and make sure the site is fully closed and healthy. I would not suggest putting dye on anything if there's an open wound or it's not fully healed. 
"This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."