I have yet to see any of the model companys' suggested painting scheme for modern American submarines on actual submarines. They are fictions of someone's imaginations. In fact, I have seen two basic color schemes aboard real boats; some are painted overall flat black while others are painted red from bow to stern on the lower half of the hull. It depends on the boat in question. Also, those rescue markings that the manufacturers provide around the hatches should only be there if modeling the boat on builder's trials, not when in commission. Your model should include draft marks forward, midships, aft and on the forward edge of the rudder. Some boats also have draft marks on both sides of the rudder as well. Masts and antennae also vary; during my service in submarines, these were painted light gray with dark gray/black splotches. At some point between my retiring in late 1996 and today, they are painted overall dark gray.
Hull numbers are hung from the top of the sail on placards when in port. They are not painted anywhere on either the hull or sail except for builder's trials. Nor are the names of the boat painted on the hull.
Flat black paints usually end up too dark, especially in these scales. I usuall mix Engine Gray with Flat Black to tone it down a little in a 50-50 mix. When I paint lower hulls red, I simply use Flat Red. I paint the propeller a mix of bronze and copper, about 25% bronze to 75% copper.
I hope that this helps. I served on six boats in my career, including three 688's.
Good luck!
Bill Morrison