Clouds come from small liquid droplets or frozen crystals of water and float in the atmosphere above the surface of Earth, or any other planet known to have a gas in the atmosphere.
Since air has water within it, water is able to exist anywhere. An invisible gas called water vapor is able to form near the ground or surface of a planet. When warm air rises due to the sun, it expands and cools. Cool air cannot hold much water vapor, so some of the vapor is compacted to form a small droplet of dust in the air. It takes several billion of these droplets to come together and create a visible cloud. Once they are formed and able to rise into the atmosphere, clouds move with the wind current. As for the color of clouds, the wavelength of the water droplets or ice crystals combined together produce a white light, giving off the color of white for clouds. However, during storms, clouds have a tendency to change colors. This is due to clouds becoming very thick and compacted, and light from the sun cannot pierce through them to give off the white color and in turn makes them appear gray.