The sideburns don't mean the red poem of begonia.

The poem that the sideburns are not begonia red means: it is not a woman who is close to you.

Begonia here refers to women, and "the temples are not red with begonia" here means that people who are close to men are not women but men. It means that the person who is close to the man is not a girl, but a boy.

Synopsis: In 1930s, Shang (Andrew), a new director of Peiping Liyuan, became an instant hit in the industry with his superb acting skills. But because he is a foreigner, he was suppressed by local forces. In order to gain a firm foothold in Peiping and realize his original promise of promoting Chinese opera, he persevered and devoted himself to the ocean of art. In this process, Cheng Fengtai (Huang Xiaoming), a newly rich businessman who had never seen Beijing opera, was deeply moved by his performance by an accidental opportunity, and he intended to make friends with him, and under his influence, he became more and more obsessed with Beijing opera.