NPC's Power rank

NPC could level up or breakthrough the next level by hunting monsters, but their levels aren’t calculated by numbers and instead by the color of their mana, starting from Red, Orange, Yellow, Green, Cyan, Azure, Indigo, White, then Gold, and the realms or grades are Third Class, Second Class, First Class, Expert or Hidden Class, Master Class, Legendary Class, Hermit, Sage, then Demigod