Yarn recommendation?

I'm planning a pair of boot socks for G, and need to find the right kind of yarn for it:
conservative in color, thick and snuggly, sock but long wearing, superwash.

I was thinking of Socks that Rock Obsidian, Terra Firma or In the Navy but I'm not sure if I should try heavy weight or medium weight. And I'm not 100% sold on the colors- In the Navy is probably my favorite for him out of the three. I have some CTH Supersock in Bark set aside for him but I'm not sure if that is too thin for boot socks.

Otherwise, I was thinking... Artyarns Supermerino? Interlacements Toasty Toes? Lorna's Laces sport?

Edited to add: I already have some Lorna's Laces Worsted in a nice Charcoal color Would that be too thick?

Does anyone know of any other kind of sock yarn that might be suitable... or if DK/sport weight would be thick enough?