The original colors were red from the keel to halfway up the hull, and black from there on up. The black is dull, sort of a charcoal dark, dark gray, not glossy. In the 1970's the hulls were usually this color as well; red on the lower half, black on the upper half.
Jack was unique, as it was the only nuclear submarine built with contra-rotating propellers. If you are in 1/350 scale, I would recommend the 3-D printed propellers specific for Jack from Mulsanne's Model Corner. I have a number of his propellers for various SSNs and SSBNs and they are far superior to the kit photoetch versions. I have close up photos of Jack's original propellers as well, now at the Albacore Museum in New Hampshire.
The other issue, uniques to Jack, was she was some 20+ feet longer than the original Permit class hull. Even the later "stretched" Permits (after Dace) were not as long as Jack. The extra space was necessary for the machinery for the complex shaft within a shaft system in Jack, as well as the gearing for the contra-rotating propellers. Longer than the subsequence "short hull" Sturgeon class, but shorter than the later "long hull Sturgeons". A one of a kind hull length. You could use a long hull Sturgeon class hull (just a bit longer), but you would have to add the aft mushroom anchor on the Permits but not on the Sturgeons.
Good luck!
Tom