This is the only one I can answer.
The sun's light is full spectrum, but when it hits the earth's atmosphere a phenomenon called Rayleigh scattering occurs. The different bands of the light spectrum are scattered by different amounts depending on their wavelength, the shorter blue end of the spectrum is scattered most and that is why it dominates the color of the sky. During sunset and sunrise the light has to travel through more of the atmosphere, and it scatters the blue so much that the red and yellow end of the spectrum dominates instead.
If you were sitting on a body with no atmosphere, like the moon, the sky would appear black at all times, even during the lunar "day".
I only know this because I had to explain it to an 11 year old during the holiday break.