re: Do you see a red coke can?

quote:

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Red and cyan are complementary colors, and the image is filled with so much cyan that when you see the area that's devoid of cyan, your brain interprets it as red.

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I'm not sure if i explained that in the best way, but it's a similar mechanism as the negative afterimage. Remember the optical illusion where you stare at a weirdly-colored image for thirty seconds and then look away at a white surface and you see the image appear in normal color? Same idea as this gif—it looks like there's a green dot moving around the circle when you're focused on the center, but if you shift your focus to the green dot, you see it's really just the magenta dots blanking out.

"Opponent-Process Theory" explains it.