Well if you're trying to be discreet, I would avoid anything with camouflage or MOLLE webbing, or anything that even looked like a gun case in the first place.
But I suppose if you're envisioning traveling about with it plainly in view, it won't matter.
My "long gun" road-tripping kit consists of an old woodland MOLLE vest, some old Desert Storm night camo overcoat/pants, concealable soft armor, and an ordinary looking hiking pack. I can wear it overtly if need be, but since probably most situations will require discretion, all that can be broken down and packed away in the backpack, and I can still have a decent level of protection wearing the armor and a pistol concealed, while looking like just another wandering bum or whatnot.
Not taking into account your local laws, have you thought about rigging it to either side of a backpack frame for quick access? Either with a non-descript scabbard (that doesn't shout gun), or something home made. Depending on your preferences, you may not even have to have it concealed much if it's mated up nicely to next to the frame or pack. Check out threads on open carry, even people plainly carrying handguns go unnoticed by most people because most people aren't paying attention to squat.
Color-wise, I think anything is better than black. Solid black isn't a good camouflage choice for day or night. Black equipment will scream "tactical" (to me anyways). Black sucks up and retains heat, which sucks in the south. I leave that color to the mall ninjas and the SWAT teams who use it for psychological value.
ETA: Now here's an interesting option....soft pool cue bags.