Why is the morning sky colorful?

The colors of the sky are created because the atmosphere between the sun and the earth consists of many different particles and chemicals. The sky directly surrounding the earth mainly consists of nitrogen and oxygen molecules as well as the dust and dubree kicked up by humans and animals on the earth's surface. When the light hits these particles, it is broken up and the different wavelengths are scattered in different directions

In the morning, the colors of the sky change. During these times of the day, the sun is positioned at a different angle to the earth than during the normal daytime. Due to this angle, the longer wavelengths are the ones that reach the eye. The blue and other shorter wavelengths are scattered millions of times and do not reach the viewer

If the sunrise of a big city is observed, it will be evident that the colors are more varied and tend to appear prettier than a sunrise in the country. This is because the sky surrounding the cities is more polluted than that around a rural setting. The pollution in the air has many chemicals in it that will break the light up in different ways and scatter it differently than the normal atmosphere would do

Source : http://www.sewanee.edu/chem/chem&art/Detail_Pages/ColorProjects_2004/Adams/Adams%20project.htm