Question

why does sky appear reddish coloured when rising sun?

Answer 1

from the rays coming from the sun red light scatters the most and the sky appears reddish

Answer 2

During sunrise and sunset, the rays have to travel a large part of the atmosphere because they are very close to the horizon .Therefore, light other than red is mostly scattered away.Most of the red light, which is least scattered ,enters our eyes.Hence the sun and the sky appears red..