At least in the 4.8.2 the Fringe Saturation parameter in Post Process Volume doesn’t seem to work at all.
I tested this issue and can confirm what you are a reporting. The documentation suggests this setting should be changing how pronounced the color shifting is for the Fringe effect. I was also not able to see any visual change. I have gone ahead and entered a bug UE-19238.
Thank you for taking the time to report this issue. If you have any further questions or need further assistance please let me know.
Apologies for bumping this question, I’d rather not start a new one. I’ve noticed (in 4.13, at least) that the Fringe Saturation option is no longer available. Has this setting been removed entirely now?
Yes, this setting has been removed.