oh i see you mean hehe...but when looked there a few them in durning war but was only used by few VIIB Type U-boats durning 1939 to 1942 was in red color sceam..but color changed in later war when Type VIIB changed color grey...
Do know anyone who can make the red hull only for VIIb or is there anyone can ask who does skin for uboats?
here some of the Red Hull German Uboats that used in Type VIIB
http://modelingmadness.com/reviews/misc/stewartu99.htm
http://modelingmadness.com/reviews/misc/jamisonu99.htm