Monday, September 10, 2012 10:36:51 PM
Odd but true and somewhat relevant to this - the cliched "ninja" outfit actually comes from Japanese theatre. Real ninjas wore whatever blended in with whatever role they were playing to gain access (e.g. unremarkable old peasant) or something that wouldn't show up if they were sneaking in at night. Which isn`t black - that creates a hard-edged shadow that an observant guard should be able to see.
Black all-over outfits were traditionally worn in Japan by stage hands who had to be in view during a play. Since audiences were very used to ignoring people dressed that way (since they weren`t part of the play) someone came up with the effective idea of using that for a ninja character to create the desired effect of a surprise appearance.