"In brightest day, In blackest
Some Green Lanterns personalize their oath. But many use Hal Jordan's.
Green Lantern Powers:
All members of the Corps have a ring and a power battery. Their rings are powered by the user's Willpower. Their rings allow them to create solid objects, shields, and many other abilities (including allowing them to fly with great speed through space). These creations are as powerful or elaborate depending on the user's level of will and imagination. If a ring's user is killed, it will fly through the universe in search of someone with great Willpower to replace its former owner. These rings require power. This power comes from a lantern in which all members of the Corps own. The user would insert the ring into the lantern (while wearing the ring) and recite the Green Lantern Oath.
While it is not required to say the oath to recharge the ring, but all members of the Corps say the oath while the ring recharges. At one point, the rings could not effect anything that was of the color yellow. However, this weakness has been overcome when they learned that they needed to overcome fear. Only trainees still have this weakness until they themselves overcome fear.
There are in total 7200 Green Lanterns that span 3600 Space Sectors.