Painted up a bannerman for both warbands today :)
I think of red as a british ground forces colour, and blue as a french ground forces colour (I think I've got that right?).
Anyway, I looked up some flags, and I chose a white cross on a blue background to keep the colours of the blue team theme. I found a red dragon flag which was Welsh, and Wales is a part of the isles of Britannia, so I decided to use the red dragon on green field as the flag theme for the red team.
(I'm not going for historical accuracy anymore, simply trying to make interesting looking medieval themed red vs blue forces)
Trying to freehand paint the dragon on green field wasn't easy, and I painted over it a couple times before I got something that I think looks okay.