tell application "SwitchResX Daemon" 
if enabled of display 2 is false then 
set enabled of display 2 to true 
else 
set enabled of display 2 to false 
end if 
end tell

you need to change the number of the display to that appropriate.

I use this in combination with a very small other script

Tell Application "Plex" 
activate 
end tell

to start and activate plex.