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On a very clear day, especially when looking 90-120 degrees away from the sun and not too close to the horizon, the sky color can approximate a "Rayleigh Blue". The above montage shows a simulation of a sky without any aerosols (top) that produces colors close to the Rayleigh Blue. The actual camera image (bottom) was taken at the same time at the National Renewable Energy Laboratory in Golden Colorado, using an EKO Instruments all-sky camera. I took the liberty of reducing the contrast in the camera image to help with color balance and reducing the color saturation. In this simulation clouds were not included.
If we convolve the solar spectrum with the inverse 4th power wavelength scattering depdence and the CIE color matching functions we can see the chromaticity value for this is about x=0.23, y=0.23. So far I'm representing the solar specturm simply with a 5900K blackbody curve. This is the correlated color temperature of the sun as seen from space. These values might be slightly different when using the actual solar spectrum.
The best place in the sky to see this is about 120 degrees from the sun since this is where scattering from aerosols (via their phase function) is the lowest. This constraint should be balanced with being up a bit from the horizon. Near the horizon the intensities of the Rayleigh scattering for each color reaches an aymptotic limit since we're looking through a significant path of atmosphere. The net result decreases the color saturation. Also near the horizon the proportional amount of aerosols along the viewing light path is larger than the gasesous component of the atmosphere. Kind of amazingly this is related to the curvature of the Earth and the fact that aerosols usually are lower in the atmosphere (smaller scale height) compared with the gaseous component.
Near sea level the sky is slightly less blue because the air is thicker and self-shadowing is more prevalant at that wavelength. The sky is also a bit less blue since light reflected off of the ground often is deficient in blue light.
Even though the actual sky color is bluer near the zenith or at a high altitude above sea level, the perceived sky color may look even more blue due to color shifting. In other words the same color of light presented at a lower intensity can sometimes look more saturated. Note that the polarization of skylight near 90 degrees scattering angle has little effect on the actual sky color, though it does contribute to a reduction in intensity.