Pigmentation post vampire facial? (Photo)

Great question.  When we do a Vampire facial, we are using your on Platelet Rich Plasma as a sliding agent and pushing it into your tissue with a mechanical micro-needling device that oscillates hundreds of times a minute to the depth prescribed by the physician.  It's like aerating your "lawn" of facial skin and adding fertilizer that helps you heal more quickly and better than you were before!  If you go deeper to get a better long term enhancement, there is some social downtime and risk of Post Inflammatory Hyperpigmentation (PIH) in skin that genetically has more underlying pigment like you have.  A skilled provider will be able to safely use most of the micro-needling devices available in the US, although there is currently only one that is "FDA approved", by Bellus Medical.
Skin is not super smart after all.  It does many beneficial things, but when it's damaged it tries to lay down collagen and elastin to heal and makes pigment if it can.  It doesn't matter much what the cause of the damage is-accidental or controlled and intentional.   
PIH generally resolves with time and care which includes you protecting the baby butt new skin from the sun (causes more pigmentation as the body tried to protect the underlying dermis from the damaging UV rays).  There are also pigment lasers and light treatments, "bleaching creams" (which turn off future pigmentation more than help fix current pigmentation) and peels to help make the pigment resolve more rapidly.
Be sure to mention this to your doc so that they adjust your next treatment accordingly and perhaps add a tyrosinase inhibitor cream ("bleach") used nightly, to your pre-procedure care for 2-6 weeks ahead of your next treatment!
Hope that helps relieve your worries.
Best, Z

This shouldn't be a permanent issue. PIH takes at least 3 weeks to be evident. I haven't heard of any long term negative effects from this procedure. There are treatments for pigmentation in the future if needed.