Question

why the colour of the sky is blue and at the evening it becames yellow?

Answer 1

heya mate!!!
here is your answer!!!!
A clear cloudless day-time sky is blue because molecules in the air scatterblue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the bluelight has been scattered out and away from the line of sight.
hope it will be helpfull!!!!