Originally Posted by
ItsonlyMeagain
They are black because they should be easier to see. The Royal Air Force learned that some time ago. Also the rotors are only partially black. They have alternating white patches, different on each blade, which should make them easier to see. I guess they just didn’t.
Me
Generally the rotor colour only makes a difference in detectability when you are above or below the helicopter. We had one yellow blade on the RAF SAR Sea Kings but that was for added conspicuity against FW traffic who might overfly SAR scenes. The blade colour has next to no effect when viewing the disc side on.