A general view
The other side and the first selector
Standard names
I got creative
even chooses your number of players how novel.
The only thing I really need to add is an arena for the two players to both teleport too and a simple system to put them on both sides and to start the second selector.
How it works is that the selectors are activated when two of the first six pressure pads are stepped on, then once all players are stepping on the plates the first player chosen teleport. On the second random selector all colours except red are there, if a colour was already chosen it is rewired to red. The small problem is that the server may have to restart in the event of needing to do a second arena selection, but this is oosos where the server restarts after each game it shouldn't be a problem.