How do you get skin like Keith?

You can't get those anymore. If you're talking about the fawn skin that Keith has, that's from Morostide back in October.

During that time you could go to the zapper version 2 and euclid would zap your HA into a skin. Those who didn't take the cure for their individual skins before Morostide was over still have their skins left over from it on their HA.