This request is in the list in pieces in various places. Some people want a "do not book" list, others want to be able to flag special guests. There are some work arounds but nothing that truly meets the needs.
I would like to see the ability to attach a color code and/or pop up to the customer which would automatically pass to any reservation. The pop up should notify us at the time of booking (during the process) not after. There are already several flags attached to the guest record which could be used. Maybe in the settings, we could indicate which ones would force the pop up or the color code.