The 'ring' is produced when light refracts off ice crystals in cirrus clouds and cirrus clouds portend worsening weather, a ring around the sun or moon is a fairly accurate indicator of precipitation within a day ortwo.
The 'ring' colors can vary. The refractive angles are slightly less for the longer wavelength of red light and shorter for the violet hues, so colored 'rings' progress from the inside to the outside band from red followed by yellow, green and violet on the outer edge. Due to the random orientation of ice crystals and the random chance of crystals hitting the light just right, the colors in most 'rings' are not very intense. Since moonlight is weaker than sunlight, the halos (as they are known) around the moon typically appear as a pearly-white ring. It's physics.
Cataracts are areas on the eye that distort light as it passes through the eye's lens, which is responsible for producing images. The lens is located behind the iris and the pupil. The most common type of cataracts are related to age which protein in the lens of the eye clump together and cloud our vision. Cataracts cause bad night vision, blurriness, problems with glare and depth perception. They usually form with age, BUT can be the result of an injury. Treatment is surgical intervention and lens transplants.