Have neither of you ever heard the phrase about the "carpet matching the drapes"? As in, "Oh you're a redhead. So does the carpet match the drapes?" Being a redhead, I've heard that far too many times in my life!
If you can get that far, I think figuring out what the door represents shouldn't take too much imagination.
At least that how I took it. I sure hope that's the joke or I just outed myself as a dirty old man.
But I did have to Google XD.