Check doing anything while player is in Lavatory:
if multi-colored door is open:
say "Polite people would close the door."
otherwise:
if multi-colored door is closed:
continue the action.
Problem message:
Problem. The phrase or rule definition ‘say “Consider what you’re about to do. […] the back room and the open booths.” otherwise’ is written using tab indentations to show how its phrases are to be grouped together. But in that case the opening line needs to be on the left margin, not indented.
But the bigger problem is that you can’t have a Check rule apply to more than one action. Every action in the game has its own Check, Carry Out, and Report rulebooks (which are generally used for the standard non-specific implementation of that action). Then there is one Before rulebook, one Instead rulebook, and one After rulebook. These are run for every* action, and are generally used to override the usual implementation under specific circumstances for your story. So “Instead of doing anything” is fine, “Check doing anything” is not.
(*Except for actions out of world such as “quit” and “restart”; you usually don’t want to mess with these.)
In this case, I would write the rule like this:
Instead of doing anything except closing the multicolored door when the player is in the Lavatory and the multicolored door is open:
say "[Text here]".
My personal style is to put as much as possible into the rule preamble, though you can also use an if-statement within the rule if you like; de gustibus non est disputandum. But the reason for doing this as an Instead rule (instead of e.g. Before) is that it will give the Check rules a chance to run. This rule won’t intercede until the action is about to succeed, in that it passed all the action-specific Check rules and it seems the player is indeed capable of performing whatever action. If you implement it as a Before rule it will take effect first, whether or not the action is actually reasonable.