This is NOT a question of color, this is a question of light vs. dark.  The upper square A appears darker because it's surrounded by three lighter squares for comparison and the lighter square B appears lighter because it's surrounded by the four darker squares.  If I lean back from my laptop and only focus on the AB with connector it does become, I do perceive it, as one continuous shade.

In the end, might makes right. Nothing has changed since the caveman.