Just to be sure, on the Quest Guide the yellow doors are doors that start open, red doors are doors that start closed, right?
Yellow Doors and Red Doors
No. Yellow doors are unlocked. Red doors are locked. Locked doors have a differently colored standee.
All doors begin closed.
Yellow doors are unlocked, meaning they can be opened using a standard action to open a door.
Red doors are locked and usually have quest-specific rules concerning what must be done to open them.
And do you know the difference between steel and wood boardgame doors?
We play like this:
yellow doors <-> wood doors
red doors <-> steel doors
Do you play the same way?
Yes.
The metallic doors are the only ones with a lock, so they are logically the locked ones.
But nothing is explicitely said in the rules - except that you have more wooden doors than metallic ones.