Source : Webster's Revised Unabridged Dictionary (1913)

Sky-blue \Sky"-blue\, a.
   Having the blue color of the sky; azure; as, a sky-blue
   stone. --Wordsworth.

Source : WordNet®

sky-blue
     adj : of a deep somewhat purplish blue color similar to that of a
           clear October sky; "October's bright blue weather"
           [syn: {azure}, {cerulean}, {bright blue}]
     n : a light shade of blue [syn: {azure}, {cerulean}, {sapphire},
          {lazuline}]