紫
むらさき · murasaki · JLPT N2 · noun
color
🍇 紫 = 糸 silk thread + 此; the purple dye came from the murasaki plant root
The kanji uses the silk radical 糸 because purple was dyed into silk cloth. The name comes from the murasaki plant (紫草), whose root yielded the dye.
紫 — 此 (phonetic) + 糸 (silk radical)
紫 is a phono-semantic compound. The bottom 糸 means 'silk' or 'thread', signaling that the character relates to dyed cloth, while 此 (cǐ) supplies the sound. It originally referred to purple-dyed silk, then broadened to mean the color purple in general.