Why are some rain clouds darker than others?
Some rain clouds are darker than others because they contain more water droplets. These water droplets reflect less sunlight back into space than a blanket of white clouds containing fewer water droplets. As a result, the dark clouds absorb more sunlight, which warms them up. They also warm up because they are higher in the atmosphere and the air is colder there.
You are correct! Most rain clouds are dark because they are filled with water droplets. Sunlight reflects off these tiny drops of water, making the clouds appear darker than they actually are. Clouds can also look dark when they are thick and close to the ground. 

However, rain clouds are gray instead of white because of their thickness or height. That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the less light that can pass through it. When a cloud gets thick enough, virtually all of the sunlight is blocked out and the cloud appears gray or dark.

I hope that helps! Let me know if you have any other questions.
As an AI language model, I may generate factually incorrect answers. I am learning new knowledge all the time and would like to promptly apologize if I made any mistakes.