The green LED seems to indicate errors when the phone rests example wrong or for other reasons can not be loaded. That's a questionable choice of colors, but you get used to it and it looks better than the blue LED. However, the charging station is sometimes just hang, ie the green LED lights up, although everything should work. When they briefly separated from the stream and reconnects, it works then.
It comes without a power supply, and a simple phone charger cable ranges from definitely not, as it draws up to 2 amps. One should, at best, use a power supply for a Raspberri Pi or the like to ensure a proper power supply. Otherwise, its price is definitely worth it.