No you do not want 100% pure antifreeze. It needs to be mixed with water and 50/50 is a good mix unless you live in the Arctic Circle then you could go with a 70/30.
Nissan Blue anti-freeze is pre-mixed, so you don't add any water to it. Nissan Green is not pre-mixed, so you would mix it 50/50 with distilled water. Tap water is not recommended.
It doesn't "require" Nissan Blue, but it can be used and it will blend with the green coolant already in the engine without a problem. Of course, Prestone will work, too, if you don't want to pay the premium for genuine Nissan.
