I get a white scum, when I use antifoam.
From what I can gather, it binds all the non dissolved solids and oil together, which kills the foam, but eventually results in slime very similar to this.
I'm now experimenting with a little critter called "ScumBug".
Within 30 minutes, all my slime had gone, although, this did also involve a little manual intervention.
I'm going to guess that one of your guests had a red costume on, or maybe red hair dye, possibly even lipstick (lets hope they weren't all men then
)