This is an unused look. This appearance has never been available on a player mount.
Notes:This grey crane is a variant of the white crane colour which appeared in the alternate version of the game database used for Chinese servers. Hopefully it could be copied to the main database and used to make a proper grey crane mount.
We don't know which saddle Blizzard would choose if they did make a grey crane mount, but you can browse all possible colours in the image viewer.