Why does Jack paint his face?

Jack paints his face in Lord of the Flies first as hunting camouflage, and the paint also gives him a mask that frees him from the rules, shame, and identity of civilized life.

The practical reason comes during Jack’s growing obsession with hunting pigs. He has already failed to kill a pig at the start of the novel, when he pauses with his knife before striking. Later, frustrated by repeated failure, he paints his face in the jungle to make himself harder for pigs to see. After putting on the mask, however, his behavior changes: he begins dancing and snarling, then draws Roger, Samneric, and other boys into the hunt.

The paint helps Jack stop acting like an English schoolboy and start acting like the leader of a violent tribe. Behind the mask, he feels anonymous, less bound by the shame and restraint that still hold back boys like Ralph and Piggy. Soon after, Jack’s hunters neglect the signal fire, kill their first pig, and return chanting, "Kill the pig. Cut her throat. Spill her blood." The face paint marks the moment when Jack chooses power and excitement over responsibility.

The pattern continues later, when Jack’s painted face and leaf crown make him look like a savage chief at the feast. The paint separates his tribe from Ralph’s more organized and peaceful way of life. Jack paints his face to hunt pigs, but the mask also helps replace the fragile rules of civilization with fear, ritual, and obedience.