I've solved it. Blue and Green Spellbooks are used at Lawful Temples, and likewise, Red Spellbooks are used at Chaotic Temples to learn the spells.

A huge thank you to the kind person who helped me out!

I'm a Lv 50 Wizard and I'm trying to learn Tier 4 spells. I have the spellbooks (Tier 4 and higher), but when I double-click them, it just says "[Nothing happened.]"

I learned Tier 3 just fine, but I'm stuck now. Am I missin…