紅
コウ, ク, べに, くれない, あか.い, くれ, もみ
crimson, deep red
JLPT2 G6 S9 F1299
糸
thread +
工
here an abbreviated form# of
汞
mercury → fabric/textiles dyed a *deep red* (compare
絳
) → *crimson*; *rouge* → *lipstick*.
[Full Kanji Etymology List]