) What is the colour of sky when sun is over head? Explain. (ii) Why does sun appear red during sun set?

(i) the color of the sky would be described with the word blue. and to be honest, I need to think about why. I'll come back then.

(ii) the sun appears red for the same reason the moon appears 8n a different color when it's close to the horizon. diffraction. the angle at which light either gets into a medium (like glass or water) is different for different wavelengths of light (what we perceive as colors).

the medium is the earth's atmosphere. if you watch a live stream from the ISS, you can see that the sunsets and sunrises look quite different in terms of color, because there the part of the light is visible which bounced back into space.

if the sun is basically above you (almost 90°) the different wavelengths will reach the earth surface on you location at almost the same angle. and they get diffuses quite a lot (the sun is actually smaller than it appears, which can be tested with a light filter). if the angle is close to 0° the wavelength plays a huge role.

(i) the blue light from the sky is either due to exited paryiclesin the atmosphere, or due to some diffraction. I don't have time for more research right now, but I would bet about 5 bucks on the first explanation