Robin Hood - I suspect he was on the scene much, much earlier - the stories, after all, set him in the very early 13th Century, but they could be even older. You're right that Chaucer mentions him in 1374, but that isn't his first time in literature - so far as I know that occurred in 1304 (in a manuscript called the Registrum Premonstratense) - and I could have missed an earlier mention. But certainly we have evidence, from 1304, that his name was known and we must assume that the mention represents a vast corpus of uncollected oral traditions. There's a good collection of lore about him in The Legend of Robin Hood by Richard Rutherford-Moore, published in 1998 by Capall Ban Publishing (Freshfields, Chieveley, Berks, RG20 8TF).
Blue paint? I don't know! We do know the Britons used woad to make a blue-dye with which they painted their faces before battle - Julius Caesar tells us that - but how effective was it? I've never done the experiment, but suspect they ended up looking as if they'd had a very bad night on the bottle. The Britons, of course, became the lowland Scots (Glasgow, among many other Scottish place names, is derived from Welsh), so it's possible that the tradition continued, though I doubt it went on into mediaeval times, and we have no evidence that the Scots (i.e. the highlanders) ever did it. As for 'Braveheart', the history in that film is so bad that it really can't be taken as a source for anything other than the fertility of Hollywood's imagination.