The source is from here.

Quest Indicators are REQUIEM's way of helping you judge the status of available, completed, and upcoming quests. They are displayed in the following ways:

Golden Exclamation Point

NPCs that have a quest available for you will display a Golden Exclamation Point above their heads. These NPCs are also represented by a Golden Circle on your Radar.

Golden Question Mark

NPCs who's quest(s) you have completed will display a Golden Question Mark above their heads. These NPCs are also represented by a Golden Circle on your Radar.

Grey Exclamation Point

NPCs with a Grey Exclamation Point above their head represent a quest who's level prerequisite you have not yet met. You will begin to see a Grey Exclamation Point when you are within 2 levels of the quest. (goldceo.com)These NPCs are also represented by a Grey Circle on your Radar.

Grey Question Mark

NPCs with a Grey Question Mark above their heads indicate that you have already accepted their quest(s), but haven't fulfill the quest(s) objectives yet. These NPCs are also represented by a Grey Circle on your Radar.

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