The tradition of archers wearing green dates back to Chaucer...

"And he was clad in cote and hood of grene.
A sheef of pecok arwes, bright and kene
Under his belt he bar ful thriftily,
(Wel koude he dresse his takel yemanly:
Hise arwes drouped noght with fetheres lowe)
And in his hand he baar a myghty bowe."