[Thanks to Carter.]This is one of the best illusions of color I've seen. The green and blue spirals are the same color! I had to use Photoshop to confirm it to believe it. Is our perception of color really that untrustworthy? Wow.
From here and originally here.
Here's a similar one, perhaps even more remarkable. The hearts are all the same color. (As usual, click on it for full version.)