You must learn a special skill to tame Cloud Serpents, which is different to the skill required to tame other Lesser Dragonkin. Pandaren hunters gain the skill automatically, but hunters of other races must learn it from the tome How to School Your Serpent, which may purchased from San Redscale at The Arboretum in The Jade Forest. You require Exalted standing with The Order of the Cloud Serpent to read this tome, but the learned skill is account-wide. You can even purchase and read this tome on a non-hunter character.
Location & Notes:
Located in Cloudstrike Dojo, Shado-Pan Monastery (Dungeon). Summoned during the battle with Gu Cloudstrike, the first boss of the dungeon. Despite its name this cloud serpent is black, not blue.