Ending 1 (Red Light)
go back a screen once you're in the screen with the end "pipe" in it. This automatically results in an inescapable red light/bad ending.
Ending 2 (Green Light)
Reading everything Mother has to say at the terminal before the end but not reading the last "terminal locked" screen will get you a green light. Also, if you do read the last "terminal locked" screen, just access the terminal again for another "terminal locked" screen and after that you can go forward and get the green/good ending.
Ending 3 (Mother)
When you reach the point where you're supposed to go down you can climb on the display sign and jump into an open vent which will lead you to the ability to reach this ending or avoid it, should you wish.
Ending 4 (Matrix)
take notice of when you get the high jump, just about right when you enter the screen where you can climb the sign to get the mother ending or when the arrow points down. Now that you've got the high jump go back to the Matrix station and then go to the rightmost gate with the rain/trees. Jump on top of the house and you'll see there's a block you can walk through. Once you've got to that point there's no going back until you get to this ending.