The feature you are looking for does not exist out of the box in any of the MainUI pages. There are some very advanced methods that you could use to get a similar behavior but you will be creating most of the framework from scratch.
If I were to try and do this myself, I would probably not even use the floorplan page, but a regular layout page with a base image underneath an svg where you can control the opacity and color of different paths that overlay a lighting effect on each room.
There is a very old post about doing something similar to what you seek in habpanel that also uses svgs, but again you are building most of it yourself:
Most of that should still work if you want to try and go that route.