As pointed out previously it is not MIL-H-5606, most McCauley Propellers are dye filled .....
http://www.mccauley.textron.com/MPC26OWrev1.pdf
On oil-filled propellers, the hub cavity is partially filled with red dyed engine type oil which is sealed in the hub and isolated from engine oil. This oil provides lubrication and corrosion protection to blade bearings and other internal parts. The oil is dyed red to aid in the troubleshooting of suspected propeller leaks