I’ll try to answer the best I can to your question.
From my personnal experience, if you use your memory palace for temporary informations, you can definitely re-use your memory palace later for other kind of informations. But, if you try to memorize more permanent information (like if you are a student or your want to study something for a long term), you should be careful and try to not re-use because your permanent memory palace will already be “full” of informations. It means that you can re-use only if the informations can be deleted inside. But of course, I always suggest to create many memory palaces
Just to be sure, your trigger is your image that should remind you the color right ? You should always be comfortable with all your triggers and their meanings before placing them in a memory palace. Use flashcards to memorize all your triggers and their meanings and then, you practice with a memory palace. If you forget a few, just go check again. The more your practice, the less you might forget your triggers.
And about visiting your memory palaces every night, yeah its kinda active recalls. What I do is I can do it with my permanent memory palaces, those who have informations I need for a long term.
For the memory palaces that I use for memory sports and disciplines, you don’t need to do it everynight if you already practice every day The main idea is just to practice often with your memory palace. The more you will practice, the more they ll be easy and faster for you to use them. So, you can either practice by memorising stuff inside, daily or just very often, or you can just visit them often to be sure to be comfortable with your locis !
I hope I answer your questions !