It's hard to say "one" material, it's a mixture between spheres of smoke in different colors and lights.. I remember i spent most of the hours with adjusting.. finetuning...  and it depends also on the scene how well it works.

I started with metaclouds, but that didn't do the trick for me. So i ended up using smoke and lights

I just reloaded the scene and the object in vue 7 and i notice it looks a little different as in 6.. 

Anyway.. i can give you the file if you like ( im not such a seller ;-)  so you can study it.. 

Material view: