Question

What color is the sky? What color are the clouds?

Answer 1

The sky is a dynamic system whose color changes with the weather, the time of day. the level of pollution, and other factors. The correct answer changes over time and depends on context.
The atmosphere is made up of many tiny and minute particles which scatters the blue light, as you may know that the sunlight is made up of 7 different colors and shorter wavelength light is scattered which is blue. But why not violet as it have the shortest wavelength among the other colors, its because the spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high atmosphere, so there is less violet in the light. Our eyes are also less sensitive to violet. So when the blue light gets scattered in the atmosphere we are able to see the sky as blue but during sunset and sunrise its different as the light has to travel a longer distance and all other light of short wavelength already gets scattered before it reaches our eyes, so the light with highest wavelength which is the red light reaches our eyes and we see the sky as red during sunrise and sunset. So the sky is blue during daytime and red at sunrise and sunset.
Some people will insist that the sky is transparent, and that it only looks blue on a clear, sunny day thanks to Rayleigh scattering.* This distinction is needlessly pedantic. There’s no meaningful difference between a thing that looks blue and a thing that is blue.

Clouds are made of water droplets, which are transparent. They scatter light and so appear to be of the color of the incident light. There are no dark or white clouds: dark clouds are poorly illuminated clouds and white clouds are clouds illuminated with white light.
During sunset, they are red because they are scattering red sunlight. The upper part appears more gray-ish because it receives less light.