An Excellent Optical Illusion
By Josh Simons on Jul 01, 2009
Assuming your aren't color blind, you see green and blue spirals in the above graphic. However, were you to download this image and sample it with GIMP, Photoshop or another image manipulation program, you would find that the "blue" and "green" are exactly the same color, RGB=(0,255,150.) I kid you not.
You can also try zooming your browser to verify that the two colors are the same. As you increase the zoom, you will notice the colors looking more and more similar.
For more like this, go here.
Thanks to Monty for this one.