Diamonds on the top is more darker then those of bottom diamonds?
No, you are wrong (if you assume, those crazy diamonds are of different color, ha ha) ..... All diamonds are identical, but it sure doesn't look like it.
The key is that the diamonds are shaded so they are slightly lighter at the top and darker at the bottom. That way, when you put them together on the paper in rows, it looks like the rows are different. [source]