noun, noun which may take the genitive case particle 'no'
steel blue; electric blue
A vivid blue color with a metallic or bright quality, often used in design and fashion contexts.
彼女は鋼青色のドレスを着ていた。
She was wearing a steel blue dress.
この車の鋼青色はとても人気がある。
The steel blue color of this car is very popular.
紺色 is a dark navy blue, whereas 鋼青色 is a lighter, more vivid blue with a metallic sheen.
Compound of 鋼 (steel) + 青 (blue) + 色 (color), literally 'steel blue color'. The term likely arose from the resemblance to the color of certain types of steel.