Note: The
original thread got locked so I'm just gonna post a new thread to help others out with this.
You need a colourset with a full/decent transparent colour for this to work, I recommend Trueno's original colourset.

The red button is simply Onactivate - namedBrick[Green_Door] - Disappear [5]
You can cancel the fade on both sides of the door by just placing an invis brick on either side. The raycasting and collision is completely optional.