“Ni” means red soil or red pigment, and the oldest red paint and paint colors were collectively called “niiro”.

Red clay is known as the oldest iron oxide pigment in mankind, and the torii gates of shrines are said to be vermillion lacquer or tan lacquer.

Although it is not a familiar color name nowadays, "ni" was one of the basic kanji characters representing the hue of red, along with ``red'' and ``vermillion.''