I always have a problem with the ways that people paint the bow. For example, one builder painted the top of the sonar dome a shade of gray, claiming that it represented wearing of the plastic dome. I have never seen that effect on real boats. I suppose the basic weathering is okay for a boat returning from deployment, but it is a little heavy. Other builders paint the bow black or a shade of gray, ending the hull red at a point before the dome. Again, I have never seen this scheme on real boats. But, to each his own.
Modelers of submarines try to create some visual effect to provide contrast and interest. But, submarines offer little in that vein. Granted, some schemes were tried in the 1960's, but these were more the exception than the rule. In one interesting experiment with color, the Royal Navy tried painting a Trafalgar class boat a shade of blue. They reverted to black.
One thing that many modelers do is to put the white markings provided by manufacturers around the topside hatches. Indeed, some photos show such markings. But, these are builder's markings only; they exist prior to commissioning and are painted over when commissioned.
I hope that it helps!
Bill