Why do the hunters decide to paint themselves with clay and charcoal?

The hunters painted themselves because they didn't want the pigs to see the. It was used as camouflage.

“They don’t smell me. They see me, I think. Something pink, under the trees.”

He smeared on the clay.

“If only I’d some green!”

He turned a half-concealed face up to Roger and answered the incomprehension of his gaze.

“For hunting. Like in the war. You know—dazzle paint. Like things trying to look like something else—”