Walkthrough
1. Talk to Wizard Mizgog. Wizard Mizgog will tell you that Wizard Greyzag's imp has stolen his red bead, his white bead, his black bead, and his yellow bead.2. Tell Wizard Mizgog that you will return his beads back to him.
3. Now this is the hardest part of the quest. Finding the 4 colored beads. To find the beads you need to kill imps. You can find imps in several places. One being next to the Karamja volcano and south of the south falador entrance. Or if your lucky you can buy the beads from other players (this can take some time to find sellers).
The picture below shows the 4 different beads.
4. Now that you have all four colored beads, take them back to Wizard Mizgog for your reward.