Dark picture and shadows

i was removing my dvd player from my cable box as it is no longer supported and was checking to see if my t.v. had the right connections in the back for the dvd player. I played around with the plugs in the back one labeled " F " and one " S " and that's when the colour on my t.v. went extremely dark. i tried fixing the problem with the menu by resetting to factory settings , didn't help . i checked all connections and plugs but nothing helped , picture is still dark and fuzzy with shadows . please help