There is a large number of providers to choose from. This should help
List of ALL scalp micropigmentation (SMP) providers worldwide | SMP Debate
Color change in pigments only really happens at those places where they dont do a lot of SMP, and so dont have knowledge of the right pigments and technique. Any of the larger specialist companies should be fine.
BTW I wouldnt go to a transplant doc, I'd go to a company that does SMP and nothing else.