I remember when each of the resorts had a "dedicated" color for its monorail station. I also remember when the boats had flags that indicated destinations, etc.
What you are relating, i.e., passengers in the front cab would be asked to move IF someone at the "home" resort requested it, did occur years ago, according to very old versions of
Birnbaum's Guide. I do not believe this is still the case since it appears the "color" coding of the monorails and boats for that matter, has fallen by the wayside. Like you BCV, I have never seen anyone asked to exit the cab in favor of another family.
As indicated previously, I believe the colors are now used strictly to delineate the individual monorail for tracking purposes by the home station.
Just thought I'd toss that out there BCV so that you had a little back-up for your memory. . .