Question: can clouds change colours

Stuart Archer answered on 25 Jun 2013:

Clouds themselves are (usually) composed entirely of water vapor that condenses (cools and turns to liquid) into tiny droplets that float in the atmosphere. Water itself is actually very slightly blue, so you could say that clouds are slightly blue too. However, because they’re most often set against a blue sky, we perceive them as white due to the amount of blue surrounding them.

You’ve probably noticed that clouds look red at sunrise or sunset? They haven’t changed – they’re still just water vapor. The reason they appear to be a different colour is the light that’s hitting them is a different colour (I’ve covered why the sky appears different colours in another question /materialj13-zone/2013/06/19/why-is-the-sky-blue-and-not-any-other-colour/).

People talk about seeing ‘grey’ clouds before it rains. These aren’t actually grey, it’s just that they have so much water vapour in them that they start to block out the light that’s trying the pass through them, shading them and making them appear darker.

Hope that answers your question!