IMO only white sweat socks and only with sneaks to very casual outings/activities. I think Thorlo makes the best sweat socks. For colored dress/casual socks Brooks Brothers, Polo, Johnston & Murphy, and Cole Haan make good socks in a moderate price range. Pantherella, Byford, and Bresciani are also great and cost a bit more. Paul Smith too- especially this season. But don't buy the really stretchy thin ones they have in the NY store. Mine are already fraying at the top and I've only worn them twice. Barney's and JW Nordstrom (as opposed to the regular Nordstrom- JW has better cotton and are worth the extra money) are pretty good too. I've found Brioni to be good, but have only bought them on sale. I've heard Bresciani makes their socks. Have had so-so experience with Zegna. Usually get them on sale also. Have had some that won't stay up and one pair I got at full price got a hole after only 3-4 wearings. Am wearing some Armanis I got at Off 5th AGES ago and they're still in great shape. Turnbull and Asser is the only place I know that sells sized socks. I've heard New and Lingwood's are pretty good too, but haven't bought any yet. They're relatively cheap online but I haven't checked the exchange rate lately. I have an unorthodox sock philosophy, and rarely wear solid colors unless they're unusually bright. IMO solid socks in the usual colors are just plain boring, especially when they're the same color as your pants or shoes. I'm with Glenn O'Brien, The Style Guy at GQ and think matching them with pants or shoes make you look like you're wearing booties. I also agree with him that you can match socks with anything, or nothing, as the mood strikes you. And I think the more often you can go with over-the-calf, the better. It just feels weird to me to have droopy socks and naked calves when I cross my legs wearing a nice pair of pants. But that could just be my own version of OCD
It's often hard to find good casual socks in particular made to fit over-the-calf.