the first one does have some variances in exact color because the image appears compressed and it caused some slight changes in color, however there is the same amount of the same color pixels in each square, all arranged in about the same pattern. I tested this in photoshop and was impressed how similar they were. I also made this quick gif that overlays square A and B to show how similar they are in color
on 3rd image, I am sure that the objects are the same color, but because it is a 3d rendering, the shadows make it nearly impossible to check in photoshop. I took 6 samples of the cross in the middle for each cross, but I never managed to get the exact same color, but the colors were
very similar, enough to prove the point the author was trying to make in the website.
just my $.02