So I had a bit of a debate with myself when it came to Tirek’s magic on this page.
 
Obviously on the show it’s orange and fiery. But in the Fiendship comic, where a lot of this is coming from, it’s sort of a purple-magenta for some reason (almost the exact color of Twilight’s magic, in fact). The only time you see orange out of him is when he tries draining magic from a unicorn.
 
Ultimately, I obviously went with the purple color. My explanation/headcanon/whatever is that purple is his base, unaugmented magic color, and the orange only comes in when he’s drained or is draining someone.