How to say "indigo" in Japanese

• インディゴ
  nounCovers the dye sense, especially the substance itself — the chemical indigotin. A katakana loanword that suits technical or commercial contexts, but a less common choice than あい.
• インド藍インドあい
  nounLiterally 'Indian indigo': it refers to the indigo plant, source of the dye, rather than the color. Less common and specific, it is seldom the word you want unless the plant is your topic.
• 藍色あいいろ
  no-adjectiveThe color word: indigo blue, the deep blue associated with the dye. Use it when you mean the color rather than the dye or the plant; it is a less common word overall.
• あいCommon
  nounThe common word for indigo as a dye. For general references to the dye or to indigo dyeing, this is the default choice; the other three are less common or more specialized.

「あい」 is the common word for indigo the dye; use 藍色 for the color, 「インディゴ」 for the dye substance (indigotin), and 「インド藍」 for the plant — all three are less common choices.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• インディゴindigo (dye)
• インド藍インドあいindigo
• 藍色あいいろindigo blue
• あいindigo (dye)