Skipjack with a Grey topside is very doubtful.. But if I remember correctly Revell also included a 3 or 4 blade screw and a "reactor hatch" and the fairwater was shaped all wrong.. The only accurate Skipjack that I'm aware of is the YMW 1/340 resin kit..
Only boats I ever saw with anything but black above waterline colors was a 598 class Boomer ( the SSBN 601 R.E. Lee) which was being being used for spec ops in the Tonkin Gulf.. The Sail and turtle back sides were painted a haze grey.
Many early 50s guppies had grey sides too but In my time on the Boats I never saw a Grey boat.. Maybe from some angles after a month or two of weathering the color may appear a greyish color but these hulls were not designed for surface operations especially the Skipjack Class. As for the red lower hulls it depends on Boat, Yard, and timeframe. I mix and match my models lower hull colors..But unless I'm modeling a Guppie or WW2 boat the upper hulls are always Black.. Just like Henry Ford's Model "T"...
For weathering I usually will add a faint greenish white "alge" waterline.. or a burnt siena color .. Once again depending on where the boat is operating and the time of year etc. and how long she has been docksided.
Otherwise there is little to weather on a modern glow boat.
Be Well/DBF
Walt