We can only assume that Silverwing was of a silvery color by the name, but it is never concretely referred to. Queen Alysanne rode Silverwing to the wall after hearing tales of their bravery and glory. She arrived on her dragon at one of the many castles that were still manned at the time but have long since been abandoned, a castle called Snowgate. She and her dragon were impressed by the Night's Watch and were very courteous and honored guests, and afterwards the castle was named Queensgate to commemorate her visit.
The Dragon refused to be ridden after the passing of Queen Alysanne and remained in a semi-wild state for decades, until she was re-tamed by the Dragonseed, one of the Two Betrayers, Ulf the White. While her rider was passed out in a tavern during the Second Battle of Tumbleton, she watched the slaughter from above, and witnessed the deaths of her kin, Vermithor, Seasmoke and Tessarion.
After the battle was over, she flew next to the fallen Vermithor, and apparently, she tried to make Bronze Fury wake up, in vain. Lord Unwin Peake declared that he would give land and fortune to any person of noble birth that was able to tame her, but no person succeeded.