An aura gradient is a chromatic indication of a mage’s resonance with the Æther Field. Generally, once side of the gradient’s spectrum is associated with lower resonance and the other is associated with higher resonance.
Though there is no rule or law in-universe that specifies how color should be attributed to magi auras, some form of visual “intensity” should increase with resonance. Most of the time however, visually, aura gradients follow the rule of cool, and is based mostly on the general “feel” of the character in question.
todo (Add some conceptual example of aura gradients below for specific characters)