Contrary to what you may think first, the blue and the green are not two different colors. Use Photoshop or any other tool to zoom in and check the exact color values. They’re the same.
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Warped field
The choice of colors is making this field of dots totally warped. But it’s not.
Some other colors may not work as well, but it’s still operating quite well in black and white.
Shades of blue
It is quite impressive to see how the eye can be tricked when hiding the shades transitions. so simple an optical illusion.
YouTube link
Not green, not blue (optical illusion)
Light green and light blue spirals seem to have different colors. But don’t believe your eyes. They really have exactly the same color (described in HTML with the following fundamentals: R=0, G=255, B=150).
Color contrast
This phenomenon is rather common when the contrast between two colours is enough to hide the similitude of two shapes or the fact that these two shapes are identical as in the example shown here (it’s easier with complex forms like these eye-shaped blocks).
