I need a way to detect which player (Player 1, Player 2 etc) wrote the most recent line of displayed text. Since player 1's name is always red and player 2's name is always blue, I'm guessing that I should be possible to detect with EUDs which player sent a message based on the color code. Obviously this has to be a shared EUD.

There is no color character in front of the player's name, so you can't figure it out based on that. Doing a string comparison with the name in the player struct obviously is beyond ideal, so I don't think there's a way to do this.

What about running individual triggers to detect which player opened their chat box and closed it using different switches/DC's for each player.

He said he needs to use shared EUDs (i.e., EUDs that will work for multiplayer), not local ones. The chat box is local.

You have two realistic approaches to take.

1) Name string comparison.

Using numerical ranges, you compare the name of a player with the name of the person who wrote the text. When the map starts, you could have a phase in which you check various factors for each name (string value, string length) utilizing ranges of values, and store the result as a death count. For each message made after that, you could do the same thing with the name of the person who wrote it, and then compare the two death count values.

2) Unique identifying text.

Require each player to begin the line of text with a character or string unique to them (such as a hyphen followed by their player number). Desync anyone who uses another player's ID. This could be made to ignore any lines written just before someone drops from the game.