The second half of the sentence "Looking back, smiling and being charming": The pink and white in the Sixth Palace have no color.
The poem comes from the "Song of Everlasting Sorrow" by Bai Juyi, a poet of the Tang Dynasty. It means: When she looked back and smiled, she was full of charm and beauty; other concubines in the palace had lost their charm.
The poet used extremely frugal language to describe how Emperor Xuanzong of the Tang Dynasty paid great attention to and pursued beauty before the Anshi Rebellion, and finally got Yang Guifei, who "looked back with a smile full of charm, and the pink and white in the sixth palace have no color". It describes Yang Guifei's beauty and charm. After entering the palace, she was favored because of her beauty. Not only did she "newly inherit the favor", but her "sisters and brothers were all from the earth".
"Song of Everlasting Sorrow" is one of the most popular poems written by Bai Juyi. It was written in the first year of Yuanhe (806), when the poet was serving as a county captain in Yumu County (now Zhouzhi, Shaanxi). This poem was composed when he and his friends Chen Hong and Wang Zhifu visited Xianyou Temple and were inspired by the stories of Tang Xuanzong and Yang Guifei.