There was a prediction some years back that a leader in a light blue hat/beret/helmet would be the one to launch the most devastating, successful attacks agains the USA. With access to a lot of the US infrastructure, a UN envoy would have perfect cover for setting up our destruction.
You're referring to Nostradamus's "man in a blue turban". There was a TV show about it once, 10 years ago or so, hosted by Charlton Heston. Supposedly the man was the "third great tyrant" foreseen by Nostradamus.
The problem with all those Nostradamus predictions is that his quatrains were deliberately obscurantist, and one can tease almost any meaning out of them.