青い
あおい · aoi · JLPT N5 · i-adj
blue
🫐 aoi = ah, oh, ee: three vowels sighed at a blue sky; ao is blue, i marks adjective
青 (ao) is the colour root and い is the i-adjective ending, so 青い = blue + adjective marker. Historically ao covered both blue and green, which is why a green traffic light is still called 青信号 (ao-shingo) in Japanese.
青 — 生 (growth/sprout) on top + 丹 (well/cinnabar) below
青 originally depicted young plants (生) growing above a mineral pit (丹, cinnabar well), suggesting the fresh blue-green color of new growth and natural pigments. Over time it came to cover a range of cool colors—green, blue, and even black—and by extension means 'young' or 'youthful.'