Answer:
The sky changes color at sunset because of the scattering of light by the Earth's atmosphere. During the day, the atmosphere scatters blue and green light the most, which is why the sky appears blue. However, during sunset, the sun's light has to pass through more of the atmosphere before it reaches our eyes, and this causes the blue and green light to scatter away, leaving yellows, oranges, and reds to dominate the sky. This is why sunsets are often characterized by warm, vibrant colors.