Brewer's: Green Gown
(A). A tousel in the new-mown hay. To “give one a green gown” sometimes means to go beyond the bounds of innocent playfulness.
Had any dared to give her [Narcissa] a green gown, The fair had petrifled him with a frown ... Pure as the snow was she, and cold as ice.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894