If you are looking to keep your head warm

I think you are right Graham. Seems more blue-ish than green in that picture. Possible the color balance was off with the camera and indoor lighting. Still, the weave looks a close match.

While searching for more pictures on Compo's hat to compare, I found this. Thought it worth a chuckle. Kudos to their cleverness.
I've seen the one Bob wears from the Winos and it's definitely the wrong colour, it should be a greenish shade.