When I was in the Army (during the OH-6, but before the MH-6), the upper rotor surfaces were generally the same color as the aircraft, and the lower surface, anti-glare Flat Black. Rotor blades are replaced after a certain number of hours used, if nicked/damaged, or as perscribed by the TM, so sometimes the colors were off by a few hues from the fuselage.
We used some anti glare black one time on the bottoms of our Chinook blades, and that stuff took on the appearance of velvet! No reflection, period! The deep black obsorbed reflection from ground lights better than any I'd ever seen, but after extended use in sand/dust/rain, etc. , the outboard leading edges started showing noticible wear.... and the LAST thing we wanted was aluminum or chromate rotor tips yelling out; "Here we are, HERE WE ARE!!!"
Take care,
Frank