The last two were the prettiest to me. Since they are lighter they would probably reflect light better. I think it would be more reassuring that the water would not be dark but it would be light. It would be nice to see what they look like in videos in other peoples pools.
The fourth is my first choice and the first is my second choice. Idk how black plaster backing will effect the water temp for you though. Our pool is a brown backing with browns & black specs, and our pool gets warm in the heat of the summer (we live in AZ).