One of my Korean students came into class wearing what initially appeared to be a rather neutral brownish-red colored jacket. As soon as he stepped into sunlight, however, the coat did something amazing: it turned red and green! I was so fascinated by this that I took several pictures--one as it first appears, and two with the sun hitting it.
The jacket, made in Korea, had tags inside (written in Korean) that listed the fabric as polyester and nylon--nothing unusual about that. But every time that he moved, the complementary colors were completely visible. Weirdest thing I've ever seen!