The color between black and white (grey/gray), or figuratively an unclear/ambiguous state (not clearly black or white). Usually written in katakana.
彼はグレーのコートを着て出かけた。
He went out wearing a gray coat.
その問題は白か黒かにはっきり分けられない、完全にグレーだ。
That issue can't be clearly divided into black or white; it's completely gray.
部屋の壁をグレイに塗り替えた。
I repainted the room's walls gray.
ビジネスではグレーな対応を避けるべきだ。
In business, you should avoid gray/ambiguous practices.