Unityのデフォルトの色
GUI.color = EditorGUIUtility.isProSkin ? (Color)new Color32(56, 56, 56, 255) : (Color)new Color32(194, 194, 194, 255);
GUI.color = EditorGUIUtility.isProSkin ? (Color)new Color32(56, 56, 56, 255) : (Color)new Color32(194, 194, 194, 255);