Luminous Starseeker

Source
This item is available for purchase from the shop or the In-Game Store for $25 or €25. It was released on August 2, 2017.

It is also included in a bundle alsong side Twilight for $30 or €30.

Mount Journal
''Energetic apex hunters of Argus, the panthara hunt by sensing the energy within living things. A panthara approaching a powerful energy source will visibly change color and become more excited.''

An energy-sensing predator from the war-torn planet of Argus, it can change color at will.
 * In-Game Store

It’s gonna be a colorful journey ''Drawing on the shifting void, fel, and otherworldly energies surrounding him, the Luminous Starseeker lets you travel in style astride this mount’s undulating hues. Saddle up, because this polychromatic beast will travel as fast as your riding skill will take you.''
 * Blizzard Shop