I don't know what Zone Stamp you are using, but as long as the Category Color radio button of the Zone Background setting is active in your MVO, you should be seeing a color.
Make sure your walls are not set to "Outlines Only" under the Floor Plan Display of the Wall dialog.
MacBook Pro Apple M2 Max, 96 GB of RAM
AC27 US (5003) on Mac OS Ventura 13.6.2
Started on AC4.0 in 91/92/93; full-time user since AC8.1 in 2004