No Photoshop tricks – This is how they actually looked.
When parts of clouds are thin and have similar size droplets, diffraction can make them shine with rainbow colors. The effect is called cloud iridescence or irisation, terms derived from Iris, the Greek personification of the rainbow.
The usually delicate colors can be in almost random patches or bands at cloud edges. They are only organized into coronal rings when the droplet size is uniform right across the cloud. The bands and colors change or come and go as the cloud evolves, and occur most often in altocumulus, cirrocumulus and especially in lenticular clouds. Iridescence is seen mostly when part of a cloud is forming because then all the droplets have a similar history and consequently have a similar size.
Sometimes iridescence can be seen far from the sun but is most frequent near to it. Much rarer iridescence is that of nacreous or mother-of-pearl clouds (also known as Polar stratospheric clouds or PSCs). They can glow very brightly and are far higher than ordinary tropospheric clouds.