Sky Blue, Why is the sky blue?

Painting on Location by Donald A. Jusko

At noon, directly over head the sun would effect the darkest blue because the ring of earth's atmospheric vapor at that angle is at it's thinnest and most transparent and ..."It's darkest next to the light and lightest next to the dark."
The dark sky color is Ultramarine Blue, an equal mix of Cyan and Magenta pigments.
The average color of the sky is the mix of Ultramarine Blue and Cyan (Thalo Blue) pigments. This color mix is equal to the pigment Cobalt Blue with all it's tints.
Pure Cyan "Phthalocyanine" Blue tints appear in the lower third of the sky. Magenta and yellow are diminished by atmosphere.

The color of water is physically present in the atmosphere, we are looking through small water molecules that are dispersed by gasses in air. This blue transmitted light filters out the opposite color yellow light so we see a blue sky as opposed to a black one. This light blue color of water molecules in the air will filter out all other colors given enough distance. From space the atmosphere looks like a blue ring around the earth, mountains in the far distance are filtered through air and appear blue.
Clear water given enough depth will appear blue, clear glass given enough depth will appear blue green.
Clear air given enough depth will appear blue as sunlight passes through water molecules.

WHY?

Seeing more atmosphere toward the horizon line will remove more Magenta from the Ultramarine blue and lighten the sky to Cyan.
We can see the effect of the atmospheres color and filter properties in any distant mountain. The light blue translucent vale of atmosphere absorbs color, turning shadow colors tints of blue and light colors higher tints with blue added.
The shadow color on the closer mountain becomes blue first than the whole mountain if it's far enough away.
This effect starts 10 yards away from you. The artist can see the color shift in that distance and will categorize two to five different concentric plains or rings in each picture. The colors values in each group are not interchangeable.

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edu., art: Paint anything in front of you with accurate colors. Use a new, different, color wheel and palette that matches the light and shadows with pigments.