In the DC Comics universe, the members of the Green Lantern Corp each wear a green power ring. Including the Green Lantern Corp, there are a total of nine different Lantern Corps. Each corp is represented by a different color. The colors of the corps cover the seven colors of the rainbow, plus black and white.
Designer "Tkamen" has created papercraft templates for the rings of power for each of the lantern corps, five of which are shown above. The PDO format templates may be downloaded here. The finished rings are rather large with a 1 1/2" (3.8 cm) diameter. I wanted a smaller scale Green Lantern ring, so I took the liberty of creating a scaled down version of the template in PDF format which is available here. Unfortunately, there are no instructions available for building the rings other than the PDO.