> By its nature, Raleigh scattering favors frequencies at the violet end of the spectrum; the shorter, the better. Your three cone types react to this mix of a little green plus some cyan plus more blue plus even more violet in a way indistinguishable from the response a desaturated blue produces: the pastel color we call sky‐blue.
Note that there exists no single spectral frequency corresponding to sky‐blue; it’s an achromatic color, however oxymoronic that may sound. You can create it by mixing white light with blue light. You can also create it with the sky’s Raleigh scattering, or with …