Great color illusion

So you think you see colors the way they are, right? In that case, maybe you should have a look at the great color illusion I received recently. What do you see in the image below? Most of us will say: “Blue and green spirals”. But are they indeed?

Now let’s remove one of the background colors, to give you a better idea of what you are looking at. First, I removed the purple background. Now you see that the spirals are indeed green, but you probably still see a difference in brightness.

So let’s remove the orange background as well. Now you can see that the spirals really are the same color! If you download the original image, open it in Photoshop and measure the colors of the spirals, you can prove that without removing any other color.