As soon as you get closer to the green door,  you notice a red keyboard strapped to the door.   Taking a closer look,  there is a wire running from the keyboard up through the door.   You think to yourself, that you probably only want to put the correct code in this keypad.  If you think you know it, then enter it now.   If not, you might want to think about trying another door.  

Maybe you should get a closer look at that keypad first.  You could also try another room.