Overcast skies, the grey that means 90% of the sun is hidden.
Cloud Cover is a cool grey.
It can be described as cool, muted, greyish and dusty.
Set in black, because black reads best on it.
Cloud cover refers to the fraction of the sky obscured by clouds on average when observed from a particular location. Okta is the usual unit for measurement of the cloud cover. The cloud cover is correlated to the sunshine duration as the least cloudy locales are the sunniest ones while the cloudiest areas are the least sunny places, as clouds can block sunlight, especially at sunrise and sunset where sunlight is already limited.
Read on WikipediaIn meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, ice crystals, or other particles, suspended in the atmosphere of a planetary body or similar space. Water, primarily, comprises the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture, usually in the form of water vapor, from an adjacent source to raise the dew point to the ambient temperature.
Read on WikipediaNoun