Cobalts are noticeably darker in appearance; given the wrap is an iron and cobalt alloy (and tbh I am assuming mostly iron because I operate on the assumption that corporations are cheap asses, though I think calling them Irons or Iron Horse strings has a certain cool factor to it, too…). Maybe there is enough in there to help slow the iron rusting 
But yeah, they are a duller greyish color compared to bright, shiny nickel. A little sheen, but noticeably different compared to the frets they cross over.
Ernie Ball says they are smooth and silky to the touch. Maybe compared to a chainsaw, sure. The person in Marketing that decided that to be a thing needs to be fired, though, or at least under review. These are the roughest strings I have touched in a long time; only the stock strings that come on my Ibanez Mikro 5 are worse… The upper 3 strings are pretty smooth, but the lower two are pretty rough. I’ve compared them to Super Long Slinkies, Dunlop Super Brights, and Stringjoy, all of which are smoother though to be fair, the thickest Stringjoy I have atm is a .090. Still, Ernie Ball needs to GTFO on calling these things silky XD My fingers were even catching on them for a while, plucking hand I attributed to maybe the tension difference but my fretting hand? Slides weren’t as easy; it took some adjustment…
And, of course, the tone, that all-important four-letter word obsessively fawned over by musicians and driven ruthlessly by Marketing departments everywhere. They do sound good. Big, harmonically rich, bright, strong. I do really like the sound of them. My setup is too out of whack still to post a decent sound clip, imo, to compare to the Super Long Slinkies I took off.
I’m not super-missing the .105 E string as much as I thought, though tbh I would still prefer these to be a .85 and .105 set on the A and E strings, respectively. I would also like them available in Super Long scale, as these just barely fit on a 35" scale bass via top load on the bridge. But Ernie Ball doesn’t seem to care for either option, going back as far as nearly a decade that I saw on their own forum, and I don’t believe I can purchase a separate Cobalt .130, either, at least from what I’ve seen from dealers that sell individual strings. Buying a 5-string and 4-strring pack is ludicrously cost-prohibitive, even trying to recoup some costs by selling the .100-.045 set which is also a hassle I do not want to deal with when restringing several basses
And my hands smell strongly metallic when I’m done playing for even a few minutes. I’ve never noticed that all that much with nickel-plated strings and I have never used stainless steel, so I can’t comment there. Just a minor annoyance with my super-sensitive sense of smell.
Edit Of course now I am finding out cobalt can be considered a conflict mineral… sigh. Trying to find out where Ernie Ball gets it will probably be hard. Though it can also come from nic kel refining as a by-product…
