What does it mean that rouge disappears when it rains?

Begonia bloom, like rouge melted in the rain.

Begonia

Dynasty: Tang Dynasty | Author: He

When it rains, rouge disappears little by little, and the half-open season is the most enchanting.

Who has a golden house to hide jiao, lock the east wind to save jiao.

Translation/annotation:

Enchanting: charming.

Begonia melts like the rouge of rain after flowering, and it is most charming when it is half open. Who can have a golden house locked in the east wind and hide this "Gillian" in it and never be defeated?

It is a wonderful idea to express love and care for Haitang with the allusion of "Golden House hides charming", which not only successfully uses personification, but also enriches the image and emotional capacity of poetry, and can further open readers' imagination and association to describe the beauty of Haitang and express their deep affection for flowers.