I just spent the week at an airstation/AFB, and while walking around the hanger one evening, I noticed the H-60’s tail rotors where “striped” at the ends. There were 3 bands, about 3" each, red, yellow and white IIRC. The main rotors had no such striping. I’ve seen this on many other types of rotor aircraft as well. Why is this? Is it some sort of visual guage? Is it to alert ground personnel of where the blades end while they’re in motion? There really wasn’t anyone around to ask at the time.
Propellers and rotors are difficult to see when they are moving. Stripes make them easier to see.
I think it is a visual guage as you suggest. The main rotor is too high off the ground to hit you so no need for the stripes. However, the tail rotor is lower to the ground and could be walked into. When the thing is spinning you just see a blur and the actual outer edge is indistinct. The stripes draw attention to the fact something is there and getting close would be a Bad Thing[sup]tm[/sup] for your health.
Just a note: Walking into a spinning rotor or prop would cause severe and expensive damage to it.
If you look at old footage of the Vietnam War, you may see some helicopters with the top surfaces of the main rotors painted variously to render them quite visible from a distance. Red and white bands were sometimes used, IIRC. This was to make it possible for friendly forces to pick out the jungle green helicopters against the background of the jungle. I recall footage of a helicopter that had one rotor blade (only) painted white or some other light color (on top). It really got one’s attention as it whirled, looking very asymmetric.
Painting the helicopters themselves jungle green made it difficult for our guys to see our own, it also helped the enemy easily pick out (and target) the green helicopters against the light blue skies. USAF dark green - light green - brown cammo on aircraft had a similar effect. :0