Your devices will be marked with different colours depending on their status. Here you can read what the colours mean:
Green Bar: Your device is connected to the network and updates permanently.
Yellow Bar: Your last changes (eg. in your playlist) are saved and will be updated with the next update interval. Afterwards this bar will be green, too.
Red Bar: Your device didn't update your playlist. The update interval was skipped and changes are not shown. The network connection might be lost. Please check your connection.