I am having an issue with alarm lamps and backgrounds for DM1. I have active DM1 alarms with the red alarm lamp bit high. On the PV750, the DM1 message is only showing the yellow background border. I have the lamp override in the DTC area set to default. The background color is set by a lamp gauge set to DM1.Current.Background which is calculated from DM1.current.lamp.status everytime a new alarm is active and everytime the event DM1.variables.write.ok transitions.

Is only the red background not working?
You could add a text gauge to the screen to look at the numeric value for the variable dm1.currentbackground, the value should be 2 for red lamp status.