When it comes to camouflage, the first thing that comes to mind is a stuck in the bushes sniper or a special-service agent in an ammunition effectively hiding him.
However, hiding your appearance can be useful not only in this case.
Some defectors are very famous, among them there are journalists, TV presenters, sportsmen. It is very dangerous for them to cross the border at the checkpoint. But they can still try. A little face-paint, a wig, a mustache and ta-dah - the disguise would impose upon even the closest friends. This set can easily change not only the appearance, but also the nationality. Change the eye shape, the skin and hair color, and eventually get the appearance of a European aristocrat.
There are, of course, different situations, but if you are lucky, border guards will not reveal the defector and let him or her through.