The Collaborative International Dictionary of English v.0.48:

Watchet \Watchet\ (-[e^]t), a. [Probably from F. vaciet
   bilberry, whortleberry; cf. L. vaccinium blueberry,
   whortleberry.]
   Pale or light blue. [Obs.] "Watchet mantles." --Spenser.
   [1913 Webster]

         Who stares in Germany at watchet eyes?   --Dryden.
   [1913 Webster]