红颜 is a literary term for a beautiful woman, derived from
红 (red) +
颜 (face/complexion) — the rosy complexion of a young, beautiful woman. It appears in the famous phrase
红颜祸水 (hóngyán huòshuǐ — 'beauty brings disaster'), a traditional misogynistic trope blaming beautiful women for political downfall, as with Yang Guifei and the fall of the Tang dynasty.