Custom debug draw color. Any color value other than UnityEngine.Color.clear (RGBA=0) will be used to render the shape.. This value is passed back when using the PhysicsWorld debug drawing. The alpha value here is always ignored. This is only used in the Unity Editor or in a Development Player. This is assigned to the current PhysicsShape.surfaceMaterial. See LowLevelPhysics2D.PhysicsWorld.Draw.