I believe I've talked about my brother's collection of GW ninjas a few times. Obviously these were originally painted black, although my favorite one, the ninja in the centre did have a 'stars and stripes' motif, a la 'The American Ninja' film [although I may be mistaken]. If you recall I thought I'd re-purpose these for use as my Light Wizard Acolytes so they all got a Humbrol Acrylic Matt white costume with elements of red, blue and yellow, much the same as the Light Wizard colours of the time.
Here's a few from behind, although when would anyone get the chance to sneak up on a ninja?
Here's the pyramid formation which makes the Light Wizard's spells more effective
So, some old school Ninjas, before the ancient and mysterious realm of 'Nippon' was exorcised from the Warhammer world!