I want my emission material to also be the colour green, but I'm not sure how to do it, here is a copy of my node layout at the moment.
Your problem comes from having the emission node strength set to 500. Anything over 1 will render white.
You can do two things to fix that.
One, the simple way is just to lower the strength of the emission node down to 1. That will make it look shadeless, but will still have your green gradient.
You can add in a node setup like this, which will keep your very bright emission source, but to the camera render your glass node. (it would still look better with the emission strength lowered.)
Notice the selected nodes, the Light Path node's Is Camera Ray output is used as the mix factor for the new Mix node. All Is Camera Ray does is determine what rays are coming from the camera.