It appears to be turning a blackish color in the surgical area.
I Had MOHs Done About 10 Days Ago on my Scalp. How Will I Know if the Wound is Infected?
Doctor Answers 2
Scalp mohs concern
It will be very difficult for you to know if you have an infection without seeing your doctor for a visit. Please make an appointment with him/her if you have not done so already. Infections may present with more redness around the surgical site than usual, greater pain in the area, swelling, or a malodorous or thick yellow to white drainage (pus). That being said, wounds that are healing normally have some redness, some swelling and some discomfort; it is all relative. And the scalp can be an especially tender area after having surgery. Make sure you are following the wound care directions your doctor has provided.
Infection after Mohs surgery?
If you have concerns about what the site looks like, it's always best to follow-up directly with your surgeon. On your scalp it sounds like no closure was done and the site was left to heal by secondary intention (very common), which means you need to keep it very clean and gooped up with Vaseline or Polysporin or whatever your surgeon told you. What you are describing could just be dried blood, but there are other options too, which is why I say any time something doesn't look or feel right, return to your surgeon for an evaluation.
"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."