'Sky blue' definitions:

Definition of 'Sky blue'

From: GCIDE

Sky \Sky\ (sk[imac]), n.; pl. Skies (sk[imac]z). [OE. skie a cloud, Icel. sk[=y]; akin to Sw. & Dan. sky; cf. AS. sc[=u]a, sc[=u]wa, shadow, Icel. skuggi; probably from the same root as E. scum. [root]158. See Scum, and cf. Hide skin, Obscure.]
1. A cloud. [Obs.] [1913 Webster]
[A wind] that blew so hideously and high, That it ne lefte not a sky In all the welkin long and broad. --Chaucer. [1913 Webster]
2. Hence, a shadow. [Obs.] [1913 Webster]
She passeth as it were a sky. --Gower. [1913 Webster]
3. The apparent arch, or vault, of heaven, which in a clear day is of a blue color; the heavens; the firmament; -- sometimes in the plural. [1913 Webster]
The Norweyan banners flout the sky. --Shak. [1913 Webster]
4. The wheather; the climate. [1913 Webster]
Thou wert better in thy grave than to answer with thy uncovered body this extremity of the skies. --Shak. [1913 Webster]
Note: Sky is often used adjectively or in the formation of self-explaining compounds; as, sky color, skylight, sky-aspiring, sky-born, sky-pointing, sky-roofed, etc. [1913 Webster]
Sky blue, an azure color.
Sky scraper (Naut.), a skysail of a triangular form. --Totten.
Under open sky, out of doors. "Under open sky adored." --Milton. [1913 Webster]