Yes, red bottom and black waterline stripe (technical term is "boot topping")
Painting the boot-top had two effects. One, was to "hide" the under-body color. But, the real reason was that oil and soot and the like from the harbor did not show as much against the black (the green scummy stuff? not so much). Boot topping often gets wider in wartime, to allow for more change in draft between full paintings.
The red color was, to an extend from the metal content in the paint to help prevent marine life from adhering to the hull.
There is a great deal of debate (the search function here will get you scads of threads to read) on what color the screws (aka propellers) ought be painted. The old builder's models had hand-crafted miniatures made from brass, so that was the color they had on the models. In real life the screws are cast in a phosphor-bronze which has a color range from a pale chocolate to a dark gold. personally, I like a dark gold with a brown--burnt sienna--wash; but, that's me, others differ.
Further, there's debate on whether the shafts from the stuffing boxes to the prop struts ought be bottom color or screw color. Painting them as separate colors is striking, particularly with those long outboard shafts. You will likely want to clear a couple of hours and go prowl the NavSource photos and make your own choice.
A note on weathering. The Iowa-class ships were flagships, they generally embarked an admiral of some sort, and the sort of staff that becoming an O-8 on up entails. Admirals and/or their staffs fond of white-washed rock neatness and ship-shape. It's also easier to keep up the paint on the superstructure while underway. So, the hull can be 'dirtier' than the rest of the ship. Places more than, oh, 12-15' up from a deck may show more wear (from not being repainted so much).
In the same vein, the ground tackle--the anchor chains and their fittings will be kept up more than they might on a smaller ship. The handwheels on the capstans probably ought be left "bright" from the photo-etch fret, as they would be polished. I like a panzer gray for the non-skid, and a semi-gloss black for the chain.
Oh, and something to watch for in the photos, some of the steel decks (like around the signal flag station) are covered in a russet-leather-colored linoleum. The linoleum is supposed to be treated with the same deck stain as the rest of the deck, but, that might depend on whether the Admiral was in his Whites or not.
Which is one of the best things about ship modeling, you can pick and choose all sorts of minutiae to include, or not include.on your kit.