Prussian blue; deep blue; dark blue; ultramarine
A deep, dark blue color; often used in artistic or descriptive contexts. The term can refer specifically to the pigment Prussian blue or more generally to a very dark blue shade.
See also: 紺青
He painted the sky with Prussian blue paint.
I wore a dark blue suit to the interview.
Compound of 紺青 (konjō, 'Prussian blue') + 色 (iro, 'color'). The exact historical derivation of 紺青 is uncertain, but it refers to a deep blue pigment.