From what I’ve observed, these two images show interesting simultaneous contrast. In the first image, the lines are the same color but with the surrounding gray and yellow makes the lines appear as the colors are switched. The lines in the yellow box are gray while the lines in the gray box are yellow. In the second image, the surrounding colors are like in the first image( in a that they are different colors from one another). But the red hand in the black box appears to be lighter while the red hand in the blue box looks darker.