Clouds can appear grey due to a few different reasons: Thickness and Density: Grey clouds often result from thick and dense cloud formations. When clouds become dense, they can block a significant amount of sunlight from passing through them. As a result, less sunlight is scattered and reflected back, causing the cloud to appear darker and greyer. Rain-Bearing Clouds: Nimbus clouds, which are associated with precipitation, can often appear grey. These clouds are typically thick and filled with water droplets or ice crystals. The increased concentration of water or ice particles within the cloud can scatter and absorb more sunlight, making them appear grey and darker in color. Shadowing and Lighting Conditions: The presence of other clouds or objects in the atmosphere can cast shadows on clouds, resulting in areas of the cloud appearing darker or greyer. Additionally, the lighting conditions and the angle at which sunlight hits the cloud can influence its perceived color. Clouds can appear greyer when viewed from certain angles or during overcast conditions when the sunlight is diffused and less intense. It's important to note that while grey clouds are commonly associated with rain and overcast conditions, cloud colors can vary depending on factors such as the time of day, atmospheric conditions, and the scattering of sunlight. Clouds can exhibit a range of colors, from brilliant white to various shades of grey, depending on these factors.