Wear the white mask of the villain

If you've ever seen a Beijing Opera, you'll surely notice that "villains" would always wear a white make-up. So this expression means you pretend to be harsh and severe. (often used in contrast to "wear the red mask of a hero", see chang hong lian)

Ex.:In my family, I'll play the harsh guy in educating our child.

Again in Beijing Opera, heroes normally wear red make-up,so this expression means you pretend to be generous and kind. (often used in contrast to "wear the white mask of the villain")

Ex1.:Don't look at that kind attitude of the old man, actually he is trying to play the good guy for his company.

Ex2.:One coaxes, the other coerces.