as artists, we need to know more than that. How to change the color of the sky that we look in different directions? Where is the darkest blue or more chromatically saturated?
Here are two photos that were taken both at 4:10 in the afternoon of April 12 in Germantown, New York. The left one was taken facing the sun, and the right was taken a few seconds later face of the sun. The clouds are completely different. Close to the sun, the clouds have dark centers and light edges. With the sun shines directly on them to the right, they are lighter at or centers and they become darker on the sides and bases. Small clouds are not as white as they have a lower vapor mass to reflect light.
The color of the sky is different, too. Around the sun is hot glare region weakens the chroma of blue, which makes it more of a dull gray-green. Looking away from the sun, blue is more saturated, which tends a little towards violet.
How do we know the camera deceives us? Is there another way to verify these observations?
I went to my local hardware store and picked up a bunch of samples of blue paint. Here's how the sky looks compared to samples of paint while facing away from the sun. A blue color charts (A) is a close match to the adjacent area of the sky. 
I wanted to photograph the samples while facing towards the sun, but I had a problem. There was no way corner them so that the sun can shine directly on them. So I set up a mirror on my car windshield to bounce the light back on swatches. 
But we can not trust this comparison because these swatches are illuminated by the warm light bounce soil and my shirt. Therefore swatches look a bit warmer than they should. This is another experiment to show how the sky becomes lighter near the sun. I took one sample of painting, he cut in two, and the symmetrical halves taped on a mirror to a device that can be called a "cyanometer." None of the samples exactly heaven. The hue and chroma are different, but the values are close in some places.
It is clear that the value of the sky darkens as we change our look horizontally away from the sun. The left arrow, closer to the sun, is the value of the lighter shade, while the right arrow, just a little farther from the Sun, which corresponds to a color chart is two steps darker. The mirror reflects another part of the sky, which also gets darker from left to right. The color changes of the sky in the value of the zenith to the horizon, too, that you can see when the cyanometer is dressed vertically. A (A) there is a close correspondence between the value of the darkest swatch and the distant sky, even if the chroma is different. Higher in the sky (B), the same color chart looks much lighter than the air around it.
The mirror reflection shows an instantaneous comparison of what happens behind us in closer to the sun region. This region of the sky is much brighter in value, while duller chroma, confirming the first pair of pictures in this post. The swatches (C) and (D) show us that the sky in the sun region remains almost the same value as it rises on the horizon, because the solar radiance increasing offsets the effect of lightning near the horizon. Let us draw some general conclusions from these observations.
- First, there are two separate systems but overlapping color gradations in a daytime sky. A system, "solar glare," is governed by the proximity of the sun. The other, "glow horizon," depends on the angle above the horizon.
- In each of these two systems the color of the sky gradates value, hue and saturation. These two systems interact with each other so that each piece of heaven gradates in two different directions at once. This means that the opaque color painter need to mix at least four separate colors starting to paint a given segment clear blue sky.
- As we move from the zenith to the horizon, the sky generally tends to become lighter, because we are looking through more atmosphere. A poet could say we looking through more sails drawn through the empty sky. Near the horizon, depending on the time of day and direction of view, sky color can range from pale cerulean to a warm gray to a dull orange, but in general it is a bleaching.
- As we approach the sun, the color becomes lighter and warmer, because a large amount of white light is dispersed at shallow angles of large particles in the atmosphere. You can see this better by standing near the edge of the shadow of a building with the sun just hidden behind the roofline. A smaller but significant relief also occurs in "anti-solar point" 180 degrees opposite the sun.
- The most dark, deep blue point that I call "from heaven," is at the zenith only at sunset and sunrise. To be specific, well the sky is is 95 degrees to the sun setting across the top of the sky. at other times of the day, well the sky is about 65 degrees from the sun.
Notes and recommended reading
Why is the sky blue? Link .
Some ideas in this post are based on Light and color in atmosphere Mr Minnaert (1954) in the Dover edition link
Minnaert and scientists as early as Humboldt built instruments they called cyanometers to observe the colors of the sky, but they were of a different design, link.
the photos were taken without polarizing filters.
