Every caster, everyone with magical potential in Rothganar, has an aura. It’s important to note before I go on that I don’t mean “aura” in pretty much any real sense of the word, but have appropriated it for my own use MUA HA HA HA HA *ahem*.
There are some people who don’t have an aura at all, and thus can’t draw power from the planet. There are some people (I call them witches) who produce their own power, little batteries of magical energy. They don’t draw from the planet either, or cast spells. A witch’s aura always shows to the Sight in rainbow colors. Trained or untrained, though, most people have the potential to draw through their auras, and do whether they know it or not. The effects might range from a slight nudge in probabilities to turning objects to gold with a touch, or giving everyone around the wings of a chicken, or extending food to cover unexpected guests.
Each person with an aura has a color, and any spell they cast takes on that color, so you might get navy-blue fire, lightning of shocking pink, or a shield that responds to strikes with green ripples. A caster will only ever see the color of their aura when producing an effect; otherwise, it is invisible to their Sight.
Auras even have some effect After the death of magic, but I’d rather not spoil things. 😉