In most contexts, clouds are white. You probably picture them as white, fluffy cotton balls because that’s how they typically look. Even in drawings and paintings, people portray clouds as round, white blobs. However, clouds aren’t always white. They can appear in a rainbow of colors, including dark colors like black and vibrant colors like pink. Some clouds may even contain several colors together.
Different factors influence how colors appear. Haze, dust, sunlight, and moonlight can all affect how a cloud looks. The type of cloud and its thickness can also affect its appearance. So, let’s look at the many colors of clouds and explore how each color exists.
White
White is the most common cloud color, but what causes clouds to look white? It may seem like they should be blue like the sky, but there’s actually a scientific reason clouds are white. Clouds are white because of the way the sun’s light interacts with them.
When sunlight reaches a cloud, it interacts with the large water droplets inside the cloud. The sunlight scatters when it reaches the water droplets, but it scatters all the colors of the sun’s light equally. So, the light being spread around is white, just like how light directly from the sun appears white. As a result, clouds look white, and the bright coloring often stands out next to the bold blue sky.
Normally, when light hits an object, certain colored wavelengths are absorbed or reflected, causing the object to appear a certain color. Yet, there are millions of water droplets in a cloud, so all types of light wavelengths are scattered throughout the cloud. All the color wavelengths combined give you white, and with all those wavelengths scattered around each cloud together, clouds usually appear white to us.
Gray
While white is the stereotypical cloud color, clouds regularly appear gray too. This is most common when there’s a storm coming. When it’s rainy outside, the clouds and water droplets inside them become thicker. Thus, sunlight has a harder time getting through the clouds, and fewer light wavelengths make their way to the bottom of the cloud, which is the part we can see. That’s why gray rain clouds may look dark and ominous to us.
When light hits a cloud, the reflected light is often sent toward the top of the cloud, making it much lighter than the bottom. In fact, the tops of the clouds always have white light in them, so they will remain white on the top even if there’s a storm. You might notice this if you’re in a plane looking down at the clouds, but from the Earth, they may look completely gray.
Black
While it’s not as common, gray clouds can get darker to the point where they almost look black. The thicker clouds get, the harder it is for light to pass through them and the darker they appear. They aren’t usually thick enough to appear black unless there’s heavy rain or snow.
Clouds might look black amid rain or snow because the water droplets and ice crystals are extremely thick, preventing light from passing through. So, like gray clouds, the clouds will likely appear white on top but will look very dark from the angle we see them. Clouds may also appear black at night when the moonlight isn’t shining on them, but that’s just because there isn’t light reflecting off the water droplets to create white clouds.
Brown
Brown clouds may provide a cool background for photos, but in many cases, the brown color comes from pollution. In some instances, it could just be a little haze and dust mixing with the cloud’s white coloring. However, brown clouds are more commonly a result of fire, smoke, and debris. Some clouds, known as atmospheric brown clouds, are just a layer of air pollution rather than traditional clouds.
For example, when burning fossil fuels and biomass, the nearby clouds may look brown because of all the particles in the air. As items like black carbon, soil dust, ash, and carbon dioxide interact with the clouds, they give them a dirty appearance. The clouds may also thicken during that process, making it harder for white light to get through the clouds.
Yellow
Like brown clouds, yellow clouds could be caused by substances in the atmosphere. Yet, since yellow is much lighter than brown, it’s often only due to a light layer of haze and dust. The sky may become yellow during a dust storm or before a thunderstorm.
The sun’s position in the sky could also affect how the clouds look. During a sunrise or sunset, the sun may appear yellow instead of white. The sun’s color can vary based on which wavelengths reach us and which ones scatter. So, if yellow wavelengths from the sun are the ones reaching us, they may also be the ones reaching the clouds the most, which can give the clouds a yellow tint as opposed to their traditional white hue.
Orange
Orange clouds are uncommon, but you may see them from time to time. Since orange is similar to a lighter brown or a darker yellow, clouds can look orange for similar reasons to brown and yellow clouds. If the orange is a dark, muddy color, it’s likely due to haze, dust, and debris filling the air. The sky and clouds may look orange following a natural disaster, such as a wildfire.
Orange clouds don’t always have to be negative. Sometimes, clouds simply look orange because of a beautiful sunset or sunrise. The sky often looks red or orange when the sun is on the horizon because the sun’s light has to travel further through the atmosphere than normal. Thus, only longer wavelengths, such as red, orange, and yellow, appear in the sky. Since the sun’s light looks orange during this time, so do the clouds.
Red
Clouds rarely look red. Yet, right when the sun is peaking over the horizon during a sunrise or sunset, the sky may appear red due to only the longest light wavelengths reaching our eyes. So, red light often appears on the bottom of clouds for a short time during sunrises and sunsets.
Like orange and brown, red may also be present in clouds during fires and other natural disasters because of the smoke, dust, and debris in the air. However, that red color may appear dirtier or red-orange rather than a beautiful bright red.
Blue
In some cases, clouds may look blueish, similar to the color of the sky. This occurs if there isn’t any direct sunlight shining on the clouds. Without light on the clouds, they reflect the color of the sky, which is usually blue during the day. This will often be a light blue or a blue-gray color.
Dark blue clouds typically occur only during the evening or night when the sky is darker. Yet, even then, they will usually be closer to gray or black than blue.
Pink
Pink isn’t a color you’d normally expect to see in the sky. The idea of pink clouds might make you think of cotton candy. However, pink clouds aren’t a vibrant kind of pink. Instead, they’re usually thin with pale pink coloring. They may also have hints of other colors in them, such as red or orange. Since pink is a light version of red, pink clouds can occur in instances where red clouds might appear.
Clouds are sometimes pink instead of red because the type of clouds and the environment affect the hue. For example, during a sunrise or sunset, the clouds may look pink instead of red if they are thin and full of ice crystals. Those types of clouds cause red wavelengths to scatter in a unique way, creating a very light red, such as pink. Certain particles in the air may also give the sky a pinkish hue, which could make thin clouds appear pink, too.
Purple
Sometimes, the sky looks purple during a sunrise or sunset because the red light from the sun mixes with the blue sky. The purple color only lasts briefly, but it’s one of the most beautiful colors to experience.
Purple hues are often visible high in the sky, above the red, orange, and yellow colors that also appear during sunrises and sunsets. When the sky is purple, the nearby clouds also appear purple briefly before other colors take over.
Rainbow
Rainbow clouds might sound like something out of a fantasy movie, but they do exist. They’re more commonly called iridescent clouds, and they can showcase all the colors of the rainbow at once. Since they don’t happen often, they usually go unnoticed, so if you spot them, be sure to snap a picture.
These colorful clouds are rare and only occur when the clouds are very thin. They’re most common in altocumulus, cirrocumulus, lenticular, and cirrus clouds. The clouds must have small water droplets and/or ice crystals that are consistent in size throughout. If the clouds are built that way, they may look like a rainbow when sunlight hits them just right.
