Nimbostratus cloud
A nimbostratus cloud is a multilevel, amorphous, nearly uniform, and often dark-grey cloud that usually produces continuous rain, snow, or sleet, but no lightning or thunder.
Read on WikipediaRaincloud grey, the sky when it forgets the sun.
Nimbostratus is a cool grey.
It can be described as cool, muted, greyish and dusty.
Set in black, because black reads best on it.
A nimbostratus cloud is a multilevel, amorphous, nearly uniform, and often dark-grey cloud that usually produces continuous rain, snow, or sleet, but no lightning or thunder.
Read on WikipediaNoun