I found two ways to do it myself:

(A) Cover up areas of the image to see what causes what to change color in your perception. Slowly reveal the full image again and sometimes A and B look alike

(B) Let your focus drift until the lines of the image get fuzzy. Look at the two squares without actually looking at them. I find that the colors look alike here. If I "snap" focus back they still look alike but nothing is fuzzy anymore.

B works better.