Diet Sprite and Sprite Zero were the exact same thing. They didn't change the recipe one bit. They just changed the name and design.

I wonder which sells better, Diet Sprite or Sprite Zero.

I think Sprite Zero. That's why they changed it.

Well, the reason why they changed the color of the bottles, too, is because they realized when there was pictures of pollution of a whole bunch of trash, and you see a bunch of green bottles, all of those bottles are Sprite. So they changed the bottle to be clear so they don't be identifiable in global picture of pollution.