Here is a redstone device I made that will create a capture the flag system 
To make using it easyer I put signs on/by the command blocks and here is the key saying what needs to be changed
(easyer to understand if you have watched the video)
1=Cords of the flag (y+1= add one to y Remember to get the cords from the center)
2=Cords of the flag and the name of the team opisite of the flag
3= Spawn for that team
4= same spawn as 3 but add 1 to y also the team name and block color number
5= team name cords of the bedrock tube add one so the y is above the pressure plate
6= team name, block color number, and the flag owners team
7= team name opisite of the flag
also when cords say <x> fix it so its just the x amount and not the <> part