A rainbow ring around the sun means that the sun's rays are passing through ice crystal in cirrostratus clouds at a 22-degree angle. The ring is called a halo.
Cirrostratus clouds are thin high-altitude clouds composed of ice crystals. A rainbow halo around the sun or moon is caused when the crystals refract the sun's white light at a 22-degree angle toward Earth. White light is composed of red, orange, yellow, green, blue and violet light, the colors of the rainbow. Each color has its own wavelength in the visible spectrum of electromagnetic radiation, and the ice crystals act as a prism to separate white into its component colors.