If I’m visually depicting magic with visible effects I tend to stick to elemental colours that have at least some resemblance to the type of magic being used.
In my fiction though (the stuff I’m using to create my board game and characters here) very little magic actually has visible casting effects.
IIRC I’ve posted 4 or 5 characters with magical abilities, and Penelope is the only one with any “Spell effects”. That’s more related to the type of magic she uses and her personality.