The picture at right (click to enlarge) appears to show a pair of blue spirals and a pair of green spirals on a red/purple background. That's what your eyes are plainly telling you.
Your eyes are lying.
Both of those spirals are exactly the same color.
I didn't believe it either, so I enlarged the picture in GIMP and examined it under extreme magnification. Those colors really are the same!
All is explained here and here.