Question

how is the colour of the sky different during the day and night

Answer 1

At day, the sun is directly above our heads and sunlight falls directly on surface. Due to this the blue light of smaller wavelength scatters and sky appears blue and red light of larger wavelength comes directly.
At night, the sun hides and the light from the sun cuts off dur to which the night sky appears black.

Answer 2

DAy

During the day (daylight) the sky has a blue appearance because the Sun’s light (white light) is made up of rainbow of colors (red, orange, yellow, green, blue, indigo and violet) of different wavelength. This means, all these different colors of light combine to give you what is called white light.

NiGhT

The black sky at night that shows you the moon, planets and stars is due to the absence of the Sun’s light. The overwhelming effect of the Sun’s light reacting with the atmosphere blacks out (conceal) the blackness of the sky (outer space). This means therefore that because there are no scattered light to reach the eyes of an observer during the night (to conceal the viewing of outer space) we get a clear (transparent) view of space, which is black.