Item quality is a measure of how rare or powerful an item is. Similar items of the same level can have different quality levels, with the higher quality items having better bonuses. The quality of an item only increases its bonuses' numeric values, there are no items whose actual bonuses change when they go up in quality.
Common items are items that have no impact on the character's combat ability. The only common items found are vendor trash and crafting materials. Food, which is bought at the merchant, is also of Common quality.
Common quality items are coloured white.
The lowest quality grade for weapons and armor, uncommon items are coloured green and can found as drops from enemies. At low levels, crafting armor from crafting materials results in uncommon quality armor. Weapons and armor sold by the merchant is of uncommon quality until the player gets badges from high-level dungeons.
Superior items are marked in blue, and can rarely be found as drops from enemies. At higher levels, armor crafted from crafting materials results in superior quality armor.
Rare-quality items are marked in purple and can very rarely be found as drops from enemies.
Note that despite the fact the Loot option in Settings does not go up to Rare, your character will still loot Rare items when they're dropped.
Legendary quality items cannot be found from enemy drops, except from Raid bosses, but can be crafted using rare recipes. They are the most powerful items currently in Grindquest.