These are iridescent clouds. The photo does not do them justice, as the colors were very bright. Unlike sundogs, which create rainbow-like colors by refracting light with ice crystals, iridescent clouds produce pastel colors, more like the colors seen in the oil films on water than like a rainbow. Iridescent clouds must be made up of very small water droplets that are all the same size. The colors are produced not by refraction, like a prism, but by diffraction, much like the colors you see on the surface of a CD or DVD.