Im not so sure about the tugs operating in war zones, they were used in ports and areas where the war came to them, tugs were sunk in enemy actions and sent to aid ships attacked. they were also armed which would of not been necessary if they were not called to defend themselves.
I do have one picture of a tug armed and in camouflage and was hoping for more to come to light.
I was thinking of building a tug and with my intrest in Naval camouflage wanted to combine the two. But the picture is of a French tug taken over by the Royal Navy and I have no details of her size, type or where built. Although she is similar hull type to the HS Class Tug (Kingstone Mouldings)