In the morning, when the sun rises, its light is scattered in all directions by the atmosphere. The blue sky is caused by a particular type of scattering called Rayleigh scattering. In the lower atmosphere, tiny oxygen and nitrogen molecules scatter short-wavelength light to a far greater degree than long-wavelength light. The net result is that the Sun appears slightly more blue than it actually is.
The Sun’s position in the sky varies throughout the year due to the Earth’s orbit around it. During winter in the Northern Hemisphere, for example, the Sun rises at a much lower angle than during summer. This variation results in different amounts of daylight at different times of year. At high latitudes (near the North or South Pole), there are periods of time when the Sun does not rise above the horizon at all (the polar night). Conversely, at low latitudes (closer to the Equator), there are periods when the Sun does not set (the tropics).
The color of sunlight also changes with time of day and season. When sunrise occurs near dawn or dusk, sunlight travels through a thicker layer of atmosphere than when noon arrives and sunlight reaches us more directly overhead. The longer path length causes more atmospheric scattering, which tends to make sunrises and sunsets appear redder than they would be if viewed at midday. Seasonal variations also cause changes in daylight coloration: during summer months in higher latitudes, for instance, days are longer and nights are shorter; this allows sunlight to travel through less atmosphere overall, resulting in less scattered blue light and brighter colors generally speaking.