An email

An email from jcmegabyte, a creator of time lapse videos of clouds...

'As for clouds and odd colors, well it's all very scientific. Believers in UFOs, government conspiracies and such will happily invent their own reasons (HAARP, chemtrails, etc.), but basically, the colors are caused by particles and gases in the earth's atmosphere filtering and scattering certain colors of light, while allowing others. This has been going on since the earth had an atmosphere - long before mankind had any ability to affect it.

The more air the sun has to shine through (i.e. at low sun angles such as sunrise and sunset), the more of the high frequency light (blues, violets) are filtered out, leaving the lower frequency reds, oranges and pinks to light up whatever they hit, in this case, clouds. This effect is even more pronounced when there is a lot of pollution (from humans, volcanoes, etc.) in the air. When the sun is more overhead, there is less air to penetrate so more of the blues (and UV) get through, causing a more white light.

Interestingly, light and water works just the opposite - blue light penetrates deeper while the reds are filtered out, causing light underwater to be virtually void of any red color unless one (underwater photographers, etc.) brings an artificial light along. '