I have the HH in Chalk - honestly, it wouldn't have been my first choice in color, but I got it during the 4th of July sale (I was so mad to find it even cheaper during their recent clearance, as well as the luggage color!!) Anyhow - I really luv the bag, BUT.... it does tend to get dirty fast. I take very good care of my bags - never place them on the floor, am cautious when I carry them, never wear them w/jeans, etc. I've only been using the bag for about 2 weeks and I did treat the bag before I started using it, and all along the side of the bag that rubs against my hip when I carry the bag is all dirty. I haven't really worn anything w/heavy dyes, so I doubt that's dye from my clothing - I just think it's "dirty" from rubbing against me, and wearing down (the other side of the bag is fine). I've also noticed a few small spots here & there - whether it was residue from lotion, makeup or whatever from my fingers - on the flap (from opening the bag), there are some small smudges.
Normally, I would go all anal at the first mark (and I did get a little upset!), but because I got the bag for such a good price, I decided to be a little less worrisome with this bag and allow it to look "worn." I don't have any intention of reselling it, so it's mine forever and I can live with it looking like I've used it.
As for the bag itself - I really really love it. If I ever have the chance to buy another one in another color, at a bargain price, I'd probably take advantage of it. The silk lining is so stunning, and the leather is heavenly. you also have to get the big fluffy tassel that comes with it - it really adds to the bag!!.
If you don't mind a little normal wear & tear, i say go for the chalk - the combination of hardware & silk lining is like no other bag I've ever seen. But if you're paranoid about getting it dirty - go with the cobalt. I'm sure you're gonna luv either one!