Iridescence.

Colour in clouds at some distance from the sun is called irisation. Splendid colour with a metallic hue can be generated. Iridiscent effect within a few degrees of the sun are the same as coronae. Iridescent clouds can be seen at larger distances (40° - 50° ) from the sun

Iridescence is created in cirrocumuli, altocumuli and in altostratus clouds. Iridescence is often seen when clouds change shape rapidly, shortly before and after a storm.