ok, i figured it, go to the last switch, watch its color and then change all the switches by clicking them to the same color as the big one, when you go out of the cave the door will be opened.
theres one purple light on mechanics underground, once u reach it what u have to do? is it kind of stepping before the right colours? thanks for the help.
 "MARDEK RPG: Chapter 2"){kind=icon}
 "Telepath RPG Chapter 2"){kind=icon}