That might be something that could be helped with the spellbook guide mentioned earlier in the thread. Actually have the guide explain that the colour of the borders are tied to the dispel type.
Something like:
Purify - This spell is used to remove harmful effects from your allies. This spell can remove magic and disease effects. Magic effects will display a blue border while disease effects will display an orange border. This spell is not effective against effects displaying a green, purple or red border.