I saw a rainbow outside Silverton, CO last week that for a few minutes seemed to show part of the color cycle (red to purple) several times within the same band. This picture is how it looked to my eye. I assume this is some refraction phenomenon of multiple rainbows, or ... ? It was also a double, but that part isn't shown.
I took another picture a few minutes later of it looking normal (the rainbow brightened, the droplets were bigger, and there was a strong double):
What is causing this strange banding?