蓝
lán · HSK 2
blue
🔵 蓝 = grass radical 艹 over 监 (lán) — phonetic borrowed from the indigo plant
Originally named the indigo plant whose leaves yield blue dye; the 艹 radical marks it as a plant, and 监 supplies the lán sound. The colour meaning came from the dye.
蓝 — grass radical 艹 + 監 (jiān, phonetic)
蓝 originally referred to the indigo plant used to make blue dye. The grass radical 艹 signals a plant, while 監 supplies the sound. Over time the meaning extended from the dye plant to the color blue itself.