Clouds are masses of tiny water droplets and ice crystals that float in the air. As such they do not have any colour. But some look white and some grey. Some change shape continously as parts of the clouds evaporate when they come into contact with the warmer air.
Effect of sunlight before sunset.
Clouds are classified mainly by apperance- dimension,shape, structure and texture.White stratus clouds are sheet like,fair weather clouds consist of piled up massess of dazzingly white clouds. They are made up of water droplets. Cirrus clouds are curly white made of ice crystals at higher altitudes, in which water droplets or ice crystals are lossly packed.
Stratus and stratocumulus clouds cause rains and are nearn earth clouds.Stratocumlus clouds are not as thick as stratus clouds and so they have light and dark arears. Sometimes these clouds are so thick that the Sun or the Moon cannot be seen through them. Cumulonimbus are the main main rain clouds which are black. This is becuase light cannot penetrate through them as they are deep and densely packed with water droplets, ice and snow particles. If we look from an aircraft, flying at high altitude, these clouds will look dazzlingly white as they reflect all lights falling on them. But for the observer on the ground the same cloud looks like black. Clouds are thus white and black at the same time.