Grey Horse w/ Short Mane/Tail

There are 2 tameable creatures with this look.

Grey Horse w/ Short Mane/Tail
Can Be Tamed
50Rockskip Falls, Tiragarde Sound
Retains its original name after taming.
Freckles canters angrily about a small island in the river west of Norwington Estate.
Available to Horde Hunters Only
50Old Drust Road, Tiragarde Sound
Friendly to Alliance. Found just across the bridge, to the east of Vigil Hill island. Only one is present at a time, but if the current one isn't the colour you're after you can kill it and it respawns quickly.

Cannot Be Tamed
50Norwington Estate, Tiragarde Sound
Friendly to Alliance and part of an Alliance quest phase. Does not seem to be visible to Horde.
* Level scaling: In Shadowlands most NPCs will scale with the Hunter's level, within the constraints of their level range. Hunters can tame regular NPCs up to 2 levels higher than them, but can only tame elite NPCs of the hunter's level or below.