Now that we know a little about light, let's apply our knowledge to the sky. The sky is a large ocean of air that actually has no color at all. The sky has a whole bunch of particles floating in it, such as dust, smoke, and ash. Particles are very tiny and sometimes impossible to see with the naked eye. When sunlight hits the tiny particles in the air, it scatters in all directions.
Blue light scatters a lot easier than red light, causing the sky to look blue.
But the sky doesn't always look blue. When the sky is cloudy, all the light waves scatter and make the sky look gray. At sunrise and sunset, most of the light waves scatter except for red, which makes the sky appear red or orange.