Colours swirl, shift and change from minute to minute. Whole domains of different sized water droplets move, grow, evaporate within the changing clouds to yield the colours.

The process appears collective, film like, but that is a deception. It is individual. Single droplets each scatter sunlight into their own sky diffraction pattern. The apparent coherence comes only because the droplets in a given domain are of similar size and each generate a similar diffraction pattern.