Oh...I empathize with this dilemma. If I were purchasing, and my hair were still blonde, I'd be going through the same darn thing.
1. The light colour is lovely, will bookend beautifully, may not show the salt as much (but might show dirt more) and may absorb dye from your jeans, as TG pointed out.
2. The camel will also bookend and adds a nice warmth (especially would look nice with your new scarf) -- but yes, it does read a bit more casual than the others.
3. Black will go with your entire wardrobe (at least the travel version I saw recently. It will lengthen the legline with black tights and pants. But it's less interesting and less fun, and shows the salt.
4. Blue would be a slam dunk for me, but not, I think, for you.
Hmmm. I think you have to order a couple and do an at-home try on. These will be a terrific addition, whichever you choose.