Like most of us meterorologists recognize that hovering slate gray clouds are a sure sign that rainy weather is approaching and that white, puffy smaller clouds signal a clear and pleasant day ahead. What the local weatherman knows that most of us may not is why some clouds are light and others dark and what the color of a cloud indicates.
Clouds are composed of tiny droplets of water that have condensed on the dust, or other particles present in our atmosphere. Though water droplets are basically transparent because the particles are relatively dense they scatter sunlight which produces the pearly white cloud color we see most often in the sky. As clouds accumulate more moisture the space between droplets becomes larger and larger, permitting more light to penetrate deeper into the cloud and the light is then absorbed rather than being reflected making the cloud appear darker. The amount of light absorbed versus light reflected is what produces cloud from range from bright white to almost black.
Clouds often take on a blue gray hue when light is scattered by rain droplets. They can turn an ominous green when light is scattered through ice and greenish clouds often signals heavy rain and hail as well as a potential tornado. Large quantities of smoke in the air produce yellowish clouds and are often the result of a forest fire.
Although clouds may appear pink, red, or orange at sunrise or sunset they don’t actually change color. They are simply reflecting the long reddish rays of sunlight that are predominant at those times of day and producing a beautiful backdrop for the beginning or ending of our day.