HONG KONG — President Xi Jinping is known for breaking the rules of Chinese politics, amassing more power than any leader since Mao.

His latest attempt to shake things up may be one of his boldest moves yet: Mr. Xi is going slightly — though unabashedly — gray, in defiance of longstanding Communist Party tradition.

For decades, Chinese leaders have sported unnaturally black heads of hair, a look that symbolized unity and gave the party a youthful veneer.

But Mr. Xi, 65, appears to be dispensing with vanity as he presents himself as a relatable and avuncular leader, part of his efforts to soften his hard-line policies.