Addressing the historical accuracy/inaccuracy discussion, the film makers were somewhat vague, (as they usually are). You've seen the movie, now read the book - for free:
http://www.legendofkingarthur.com/
He's a man willing to put his money where his mouth is:
http://www.prnewswire.co.uk/cgi/news/release?id=14389
As for Guinevere's outfit - if she were only wearing blue paint ... well then, that would have been that much more historically accurate, wouldn't it? The only problem I see in this approach is that they all would have been naked. Personally, I would have appreciated just a touch more realism.