His hair was the Pompadour Wig you can find in the game. He's a disguise expert who goes under constant surgery and outfit changes to spy on multiple factions. You can find him disguised as a Diamond City guard when you first arrive at the city, as a wastelander inside the pods at Goodneighbor the first time there, and as a caravan guard in Bunker Hill, too.
All before you meet him officially. He has unique response dialogue if you approach him in all those spots. But don't go getting surprised - it isn't Bethesda actually pulling off the character well, they're just little details like the skeletons and teddy bears they place around. Nice little touches, but insignificant in the long run. Now maybe if they made a good game to go with these touches, that would be better.
Just to note, though - plenty of his dialogue as a companion are lies, such as claiming to be very old or the original leader. You can reveal this through a Charisma check. Turns out, he's just a really good liar because he's supposed to be a spy. Not sure if stupid or a rare breed of excellent.