A science project that explains the blue color of the sky at certain times of the day can be done by projecting a beam of light from a flashlight or a projector through a transparent container, like a large beaker or a jar, filled with a mixture of water and some powdered milk. The beam appears bluish-white when viewed from the sides of the container.
The phenomenon of scattering of light, known as Rayleigh scattering, is responsible for the blue color of the sky during the day and the reddish-orange color of sunsets and sunrises. The air in Earth's atmosphere scatters the shorter wavelengths of light, which is the blue end of the visible spectrum, a lot more effectively than the longer wavelengths, which form the red end of visible spectrum. This is why the beam of light in the project appears bluish-white from the sides. The blue light has been scattered more and can reach the eyes, which is why the sky is blue during the day.
If the beam is viewed from the opposite end of the container, it appears to be red. This happens because most of the colors except red have been scattered and cannot reach the eyes. During sunsets and sunrises, the sunlight has to travel a longer distance than during the day, which means that most of colors of light other than red are scattered, making the sky appear reddish-orange. Also, violet is the color that is scattered the most, but the sky does not appear violet because the eyes are better at perceiving blue than violet.