Equipment above blue grade will have at least one extra grade attribute. You can use the Refine function to get additional attribute.
How to refine
Click Refine in the Armory in any main city to enter the interface. Drag the equipment you want to refine in corresponding places.
Click the button to start refining. Gold or gift coupons are required for each refining. The attribute will be renewed afterwards, but the grade will remain unchanged. You can choose to continue refining if you are not satisfied with the result.
You can receive Free Refining Stone in the game. Freerefining tries will be used first. You'll need to pay gold or gift coupons when free refining tries are used up.