If I ask you what color is the sky, you will probably say "blue".
(I don´t mean at sunrise, sunset, or on a cloudy day.) You are right. But, an artist sees several shades ( temperatures) of blue and so can you if you observe carefully.
It´s all about knowing what to look for!
Look at the beach photo I took. The strata of clouds make it easy to see the separations of the blues.
Why does this happen?
Think of the sky as a dome above you. Right above your head, there is less atmosphere (curtains) and the point is closest to the darkness of outer space). As you descend your gaze and move it towards the horizon, more curtains of atmosphere are coming between you. ( See previous posting for explanation of curtains of atmosphere.)
So, right above you is the sky´s true violet-blue, then it very gradually assumes a true blue, then a green-blue and eventually along the horizon a rose-grey haze.
Another interesting thing about skies... Look at the "holes" inside the folage of a tree. Inside these "sky holes" the sky looks bluer.
Don´t take my word for it. See for yourself. I hope the sky will never be just blue for you again.