In a comment at Hugo Schwyzer's post about his academic journey, Mark O. Daniel, a high school English teacher, wrote:

I've been reading"Huck Finn" with my sophomores for over ten years and we've been mystified by the scene where Jim's face is painted blue to accompany the"sick Arab" sign. Recently, during a presentation on the Crusades, a slide was shown. An Arab with a blue face was contending with a crusader. Can you or anyone shed some light on whatever connection there may be here?

On Friday, Brian Ulrich and Richard Morgan posed several possible explanations. Now, via e-mail, Juan Cole says:"... some Berbers in Morocco paint their faces blue in war. Twain would have known that. I don't know of any group in the Levant during the Crusades that would have."