It is a dark blue-green color that resembles the color of iron-burnt skin. It may also refer to the dull blue color of the glaze Kuresu. Japanese says Kuro-gane-iro. > example products for metal > example products for colors くろがねいろ 漢字
It is an element with atomic number 26. The element symbol is Fe. It is the second most abundant on the earth after aluminum, and is produced as hematite, magnetite, limonite, iron sand, etc. It is old difficult Kanji character. Japanese calls Tetsu and Kurogane. > example products てつ くろがね 漢字