This is an unused look. This appearance has never been available on a player mount.
Notes:Unlike the Imperial Quilen this mount doesn't have flying animations. It was designed for Mists of Pandaria but never made available to players.
Incidentally the art depicted here could be used on the flying model, as the skin formats are identical. There's no wing art designed specifically for this colour, but that comes from a separate file and it could easily use one of the four established colours.