I should point out that I have China Glaze Sugar High on my pinkies in these photos with one coat of either polish on the top.
Grapefruit Fizz is a sheer yellow pink with a kind of small pink flaky in it that flashes bronze/gold. This makes a fantastic layering shade over any pink, even purples, corals and oranges. Not sure how it'd be over other colours, say a blue, it might be worth a go! This does have a very very sweet scent to it - not sure if its grapefruit as I don't know what one smells like, but it is very sweet, almost like fruity bubblegum. I have written in my notes that I stopped at three coats as it was getting a bit gloopy, so I think my ring and index finger has three coats and my middle has four. It would take four to five coats to hit opaque. I'm pretty sure these are designed to be layered though.
Watermelon Fizz Pink is a sheer orange red with pink flaky that again flashes bronze/gold. This one is a little more pigmented than Grapefruit. It also definitely smells like watermelon, I was actually suprised when I got a whiff! This is opaque in three to four coats. I have three coats on my nails. Again this is great for layering on reds, pinks, oranges, corals and purples, but some experimenting would have to be done for other colours. I also have written in my notes "makes me want to eat my own fingers!" haha.