Rare - Blue
Epic - Purple
Legendary - Gold
The rarer an item is, the harder it is to find and consequently, the more value it has. Upgrading your gear will increase its base stats.
The same rarity levels apply for the equipment of the Adrestia, your ship. Upgrading pieces of equipment on your ship will increase their effectiveness, as well as the rarity level.
If you have any questions, feel free to contact us!