Bottom line: Zhonglang Lv Qi, Taishi Huang Ting.
This couplet uses four colors of blue, red, green and yellow to render four famous people in Tang, Song, Han and Jin Dynasties. "Bachelor Purple" is a great poet in Tang Dynasty. Li Bai, a bachelor of Hanlin Academy, is a purple layman. Shang Shu Hong Xing is a famous Shang Shu Song Qi in Song Dynasty, who got the good name of "Shang Shu of Red Apricot" because he wrote the famous sentence "Spring is full of branches of Red Apricot". Lv Qi, a corps commander, is a calligrapher of Han Dynasty, Cai Yong, who is good at Qupai and drum set. Luqi, the name of Guqin. "Taishigong Huang Ting" is a calligrapher in the Jin Dynasty, who studied under Wang Xizhi, a literary historian, and once wrote Huang Tingjing.