The repetition of the word "green" here allows our sense of the scene to fold in upon itself, almost as if the fog of green stuff is surrounding us as well.
The long "ee"s of green lengthen the time it takes us to read the lines, slowing our tongues down slightly.
It's like those scenes in horror movies that suddenly shift into slow motion: what's going on here is so awful that we have to pause in order to take it all in.