Considering that shorter wavelengths scatter to a greater extent in the atmosphere, I would expect there to be a greater proportion of blue light from a clear spring sky than a summer sky due to the lower angle of the sun in the spring. However, there might still be more blue light overall in the summer simply because the light intensity is greater. I would also expect that slope position, relation to nearby objects, and cloud cover would influence the relative intensity of various wavelengths coming from the sky at any given time.