Blizzard is changing Season 4 Keystone Master mount to purple, as they agree that the color scheme is too close to Season 2's mount!
We’ve received and agreed with a lot of feedback about the color scheme for the Keystone Master mount for Season 4. It did look too similar to the Season 2 Soultwisted Deathwalker mount.Our art team has updated it so that the colors are more unique, like the other Keystone Master mounts. Read more on wowhead.com