'Tete de negre' appearance of the skin is seen in:-
Antemoem Abrasion
Superficial burns
Drowning
Purrefaction
In drowing, with onset of putrefaction, skin of head and neck become dark with 'tete de negre' appearance (Tete de negre is the French name for a desse, a pastry covered with black chocolate, which literally means 'nigger-brown' color.)
Drowning