Whether it is moonlight or starlight, at night, its light only shines from the other side of the earth, which is relatively dim. If it is these two kinds of light, the clouds we see are usually black, not white.

We can see white clouds because the lights of big cities are mapped to the sky, and then the white clouds are reflected to the ground, just like we see things with flashlights at night. By reflecting the light of the flashlight, we know what color the object in front of us is.

This cloud is relatively low from the ground,

More often, it appears around 15 in the old calendar. When the moon shines high, it is supplemented by moonlight shining on the other side. That is, both sides of the cloud are illuminated by light. (That is to say, what you actually see is the color of moonlight)