Tastes Like Purple-There’s a bad Princess Twilight Sparkle joke in here somewhere, get your head out the gutter.

Overuse of magic has synesthesia as a major symptom.  Cases of hearing colors, tasting musical notes, smelling sounds…when the local magical field gets overloaded, senses and perceptions get mixed up for a while.  If you’re suddenly able to taste soprano notes, it’s time to find solid cover and hope that more serious problems, like diarrhea, odd mental conditions, or the localized breakdown of reality doesn’t happen.