Bristle green

Quick answer：

Bristle green, also known as copperas green or verdigris, is a green pigment that forms on the surface of copper and bronze when they are exposed to the atmosphere. It is a basic copper carbonate hydroxide, Cu2(OH)2CO3, and is commonly used in painting, art, and as a fungicide. The color ranges from bright green to blue-green, and its intensity depends on the thickness of the layer and the composition of the metal surface.