Understanding how clouds are displayed from satellite visible images

During the day satellite views show a visible image. Clouds are white, and the surface underneath is darker. Visible pictures are helpful because they show low clouds and fog very well.

When the sun starts to go down the Western side (daytime) shows a visible image and the Eastern side (nighttime) shows a fog product.

The image below shows both day and night. Notice how during the the day (left side) you can see the ocean and can tell there are very few clouds, but the night (right side) the red arrow points to the same cloudless sky but is shown as flat gray. High clouds appear black.