I notice a lot of truck guys have brake rotors that are rusty. I have a 2007 Titan and mine were that way from the dealership, but if you install new rotors, they need not stay that way.
Hot Rodders have known a trick for years. Simply spray the new rotors with engine enamel paint, after cleaning thenm of course. No point in spraying them with paint if they have oil on them! I just put new rear rotors on my 2002 Camaro SS and I sprayed then with enamel in a color called "ceramic" which turns out to be a silver look.
Spray the entire rotor surface including the area where the brake pads will touch. Let them dry for a day or two. When you perform the first stop, the brake pads wiill clean off the paint only on the area where they touch. The rest will still look new years later. I did my Camaro's front rotors on 2005 and they still look brand new after a winter in Idaho, one in Austin, and another in Irvine.
if it's just sitting, spray the whole assy. with some penetrating oil..
..:rockon .DOT3 brake fluid does wonders for storing/restoring quality chrome...a rag soaked in DOT3 fluid, clean or dirty, will whipe off just about any combination of road-dust/grease-mud that you'll find under your engine.
..."Breakfee" gunoil performs best on both accounts.
..:informati .wear rubber gloves until your done breeding.