Because the points in pcolor are not the colored tiles like you'd expect - they're the lines. Did you ever notice that you don't have a colored tile for each of your elements? If not, try this
m=magic(4);
pcolor(m); % Shows 3 by 3 array, not a 4x4 array.
I suggest you use image() or imshow() instead of pcolor unless you know for a fact that you want pcolor for some reason and are aware of its quirks.
