Strange Balao skin
 

In May '44 I was offered a new sub and gladly left my trusted USS Gunnel to take command of the USS Tang :D, but when I took her out I was really surprised: The skin wasn't the typicall blueish-greyish colour but she was pitch black! Why the heck did they paint my sub black? Does SUBCOM think I need an extra challenge?
Did somebody else encounter that 'problem'?