I am just thinking here, Aurinax is supposed to be an Ancient Gold Dragon, and to quote D&D 5th Edition Monster Manual "The most powerful and majestic of the metallic dragons, gold dragons are dedicated foes of evil.
A gold dragon has a sagacious face anointed with flexible spines that resemble whiskers. Its horns sweep back from its nose and brow, echoing twin frills that adorn its long neck. A gold dragon’s sail-like wings start at its shoulders and trace down to the tip of its tail, letting it fly with a distinctive rippling motion as if swimming through the air. A gold dragon wyrmling has scales of dark yellow with metallic flecks. Those flecks grow larger as the dragon matures. As a gold dragon ages, its pupils fade until its eyes resemble pools of molten gold. "
The metallic flecks get bigger as the dragon ages, and merge together, Previous editions actually stated that "a great wyrm, would look as if cast from solid gold." So other than a few other colors for claws. talons, mouth, and teeth, this gold color is just gonna get shinier. When he is finished he'll get an overall gloss coat, not a matte coat.