Mehndi is Urdu for Henna. Girls apply it on hands, feet etc to get a brilliant red color patterns. It is also used as a natural red hair dye. Men also use it to dye hair in Pakistan. Starting from North of Pakistan it is quite popular among men. The preference changes to black dye in the mid but I think it becomes popular again the south. Islamabad is located just about at the cross roads of North an Punjab so both colors can be frequently seen.
Meet Tariq Shah, who likes to dye his hair red with henna:
And see how he stands out in a gathering:
By the way I do not dye my hair.