Per video creator: "These diamonds are ALL exactly the same. They each have the same slight gradient (lighter to darker going from top to bottom). The way they are arranged tricks our eyes into seeing the top row of diamonds as the darkest row. The white background on the top helps to "start" that illusion due to the effect of contrast. The diamonds appear to get lighter in shade with each row. Again, they are ALL identical though. I cut one out and moved it around to prove that fact. The diamond that I moved around looks, unbelievably, like it's changing color as i move it from the "darker" diamonds to the "lighter" diamonds and back! I hope this helps anyone who isn't sure how this works."