Those two shades of red Stick mentions really aren't red, at least not the top one. The paint color, when applied to the hull is a neutral-medium gray. Some weathering etc., has given it a reddish look in that photo, but the base color, shouldn't start with any red.
Ditto on the numbers and hatch markings, they are there for initial sea trials and then gone. You will have depth markings though.
In service submarines, tied at the pier, are usually some of the ugliest naval vessels you can see. I imagine that's why you rarely see a model of one done that way. Plus sub photos on the Navy's news site or rare too, for obvious reasons.
Doing a realistic looking, weathered boat, would make an interesting project, particularly in 1/700th scale. The weathering would need to be blended for the right scale effect, but it could be an ugly display when finished. Submariners would get it, but I wonder how many casual observers of the model would wonder why the modeler would want to show how, "badly he painted that model."
Maybe that's why you don't often see them that way. I might have to try it though.
Have fun with yours.