See if you can figure out how this is done (see below the video for answer).  It’s not a camera trick and it’s not lighting.

If the diamonds were all the same color, then you shouldn’t see shapes at all – it would just be one solid color on the piece of paper. Yet we see diamond shapes. So how is it that they are proven to be the same color when compared to each other?  The reason is, the diamonds are the same, but they are not solid colors.  They are all the same gradated shade of grey; the top of each diamond is slightly lighter than it’s bottom.  You can see this if you put a pencil across the center of a row of diamonds. We see the diamond shape because the top (lighter) shade of each diamond is meeting the bottom (darker) shade of one above it.