Let's fix and simplify it. Brand is only for weapons, ego is a more general term.
Blue : potentially have an ego, or have one.
Green : runed/glowing but no ego. Has an unidentified enchantment.
Dark Grey : unusable.
Red : cursed, bad or hated by god.
Bright Green : uncursed and equipped.
Bright Red : cursed and equipped.
White : artefact.
Purple : dangerous.
Yellow : emergency.
Cyan / Light Blue : good.
Grey : default
Purple items don't prompt before use. They are immolation, torment, mutation, crystal balls. You only get a prompt before using a tome of destruction or memorising from a dangerous spellbook.
By the way, I made a
wiki page about that some time ago.
What about spells? I'll have a look into it.
<+Grunt> You dereference an invalid pointer! Ouch! That really hurt! The game dies...