That's not a fez, but a tarbuz. So the trooper is a 'regular', that is, a member of the 'regular indigenous troops' - in the early S. XX, native troops (saharaui) commanded by Spanish officers. Since the defection from Sahara, Regulars are manned by spaniards.
As a sidenote, a classmate of my father was assigned, as a brand new 2nd Lt, to a Regular Tabor (regiment). The first day, he had to witness the autopsy of one of his men. The young officer was looked with indulgence by his seniors when he often doubled over his tarbuz, obviously to puke in it. When the autopsy was over, the colonel had a close look at the poor guy... and found the tarbuz half-filled (then) with brandy.
Credidi me pulcrum felem vidisse...