Literary, evocative - favored in fiction, poetry, and travel writing. Common collocations: 暮色苍茫 (vast hazy twilight), 暮色四合 (twilight closing in from all sides), 暮色降临 (twilight descending). For neutral 'evening' use 傍晚.
memory
暮 = 日 (sun) sliding under 莫 / 艹 - picture the sun setting into the grass at the day's end. Pairs neatly with 朝 (morning) in compounds like 朝暮 (dawn to dusk).
