Unfortunately this is not possible.
You can somehow have different formatting conditions for the whole cell (or the entire row), but not within cell’s items.
However, for what I understand from, you could shift down by one level of cardinality and have rows containing the single attendee (and group them subsequently by invitation event, for instance).
In that case, the formatting would be straightforward.
Hi Ross, welcome to the community (and I’m sure we talked before )
You cannot apply conditional formatting to individual list items in a cell via Coda UI. But you can employ some hidden formula magic to e.g. set colors and highlights via formulas (note that setting highlights based on kr-* classes is unsafe and care should be taken when composing such formulas):