there is a section of "Status icons" in the Map Designer where you find icons which change the color, e.g. "StatusOnly XL", "TrafficLight" or "Sizeable icon on Status Related Background".
If you select a single sensor, the whole baground get green , yellow, red depending on your sensor status.
If needed you can also put then a custom transparent icon (e.g. by custom HTML you can load any graphic into the map) in front of this sensor and get changed the color then by the sensor icon from background.
Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.