One of the rewards for the Dawn of the Infinite megadungeon are Infinite-themed Dragonriding customizations, giving your mounts a dark gray scale customization.
With the latest Patch 10.1.7 PTR build for Fury Incarnate, the Infinite customizations have been expanded! Learning the manuscripts that drop from Chrono-Lord Deios now also grant Infinite-themed customization options for Eye Color, Hair Color and Horn Color for all five Dragonriding mounts.