Good way to stylize some items?

[rieje]

I have a tmux-sessionizer script that lists sessions which include both running sessions and pre-defined sessions (start a session with a pre-defined layout). I want to differentiate the running sessions that get listed first.

I'm not a fan of adding additional text e.g. prepending/appending running session names with an asterisk because it messes up the formatting/readability. Adding a ------ to the menu is also not ideal because that is an item itself.

Ideally there's a way to stylize a subset of items without introducing added text/items, e.g. coloring these items (assuming you can do that and I'm not sure if parsing the selection needs to account for that) or the gutter next to these items.