See the blue and green spirals in images below? Behind the orange and purple stripes? …. Well apparently seeing should not be believing, because they are the same color! [Verifiable with Photoshop]
More color illusions at http://www.psy.ritsumei.ac.jp/~akitaoka/color12e.html
Very interesting indeed. Perhaps it would be more interesting if this were a vector image instead of a compressed gif.
I had a look in photoshop and the lines that appear blue have a bluer line around them thanks to the purple stripes, while the lines that appear green are given a more yellowy tinge thanks to the orange lines.