Xstitcher, the green one's my fave too !! They're actually pretty easy to make.
We did these in class using balloons ( on those sticks you use for helium balloons,so you can let the air out later )
You make up a batch ( or more depending on how many colours you want ) of gelatine in a bowl - mix in the colour ( my green is a pearlised green ) & you need to keep it warm( we used an electric frypan with water ) - too hot & it's too runny, too cold & it's too thick to coat the balloon.
You swirl the balloon around in the bowl a few times until it's coated with the gelatine ( takes a few goes to get it smooth & bubble free !! )
Let it set for 1 -2 days before deflating & removing the balloon
I hope I've explained it clearly !