Green cloth was made in Lincoln and was called Lincoln Green in the 15th century. Graine may mean scarlet but also can describe a quality of the cloth rather than the colour.
If all in scarlet, a very expensive cloth, why then would the ballads distinguish the times when Robin was wearing Scarlet as opposed to the Libcoln green of his men?
Green was the accepted colour for Foresters and would obviously have been the appropriate colour for their outlaw opponents.
Chaucer describes a Forester in his Prologue, please note the colour of the coat and hood.
101: A yeman hadde he and servantz namo
102: At that tyme, for hym liste ride so,
103: And he was clad in cote and hood of grene.
104: A sheef of pecok arwes, bright and kene,
105: Under his belt he bar ful thriftily,
106: (wel koude he dresse his takel yemanly:
107: His arwes drouped noght with fetheres lowe)
108: And in his hand he baar a myghty bowe.
109: A not heed hadde he, with a broun visage.
110: Of wodecraft wel koude he al the usage.
111: Upon his arm he baar a gay bracer,
112: And by his syde a swerd and a bokeler,
113: And on that oother syde a gay daggere
114: Harneised wel and sharp as point of spere;
115: A cristopher on his brest of silver sheene.
116: An horn he bar, the bawdryk was of grene;
117: A forster was he, soothly, as I gesse.
