noun, noun which may take the genitive case particle 'no'
A gray color like that of a mouse or rat; a common color term in everyday Japanese.
彼はねずみ色のスーツを着ていた。
He was wearing a dark gray suit.
空がねずみ色に曇ってきた。
The sky has clouded over to a slate gray.
灰色 is a more general term for gray, while ねずみ色 specifically refers to a dark, brownish gray like a mouse's fur.
Compound of ねずみ (mouse/rat) and 色 (color), literally 'mouse color'.