From the Tang scholar Li Jun's 《
摭异记》 (Zhāyì Jì):
国色朝酣酒,
天香夜染衣 — 'her national-grade colour drinks the morning wine; her heavenly fragrance dyes the evening robes.' Originally a tribute to peonies (
牡丹 mǔdān), and Luoyang's peonies in particular. Later extended to extraordinarily beautiful women, the way English borrows 'a Helen of Troy'.