Usually the sky looks blue and not pink or red or green or yellow.
It looks blue because sunlight passes through the air.
Sunlight is made up of all the colors of the rainbow.
When they pass through the air of the atmosphere, these colors diffuse.
Some colors diffuse more than others.
The color that spreads the most
is the one you see in the sky: the blue.
Usually the blue of the sky is a light shade.
But if you get on a plane
several kilometers high,
you will see the sky dark blue,
because between you and the sun there is little
air that diffuses colors.
If in a space rocket
you ascend even higher than a plane,
you would see the sky so dark it would seem black to you,
because so high there is almost no
air that diffuses the colors.
Sometimes the sky doesn't look blue.
When dawn and when evening falls,
the sunlight diffuses in such a way
that the sky looks red, orange or other colors.