Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the cloud, hence the gray or even sometimes dark appearance of the clouds at their base.

Thin clouds may appear to have acquired the color of their environment or background, and clouds illuminated by non-white light, such as during sunrise or sunset, may be colored accordingly. In the near-infrared range, clouds would appear darker because the water that constitutes the cloud droplets strongly absorbs solar radiation at those wavelengths.