Red or Green?

I was having a really awesome dream this morning.  An old teacher or puppet master painted a few, red brushstrokes onto a blackboard, to simulate a door.  Then the door filled in, and I wondered, "Did he finish it, or did the door complete itself?"  The door became more three-dimensional, projecting from the chalkboard.  The man then started to turn the chalkboard on an axis, which would reveal whatever was behind the door.

Then the frickin' alarm clock went off.

I won't tell you the song which was playing in the background of my dream, partly because it wasn't at all relevant to the red door, but mostly because, if you could reach me, you would hurt me.  Instead, have this song about a door.