the green light means if the Quad is in power saving mode (600s with no button pressed, Quad will get in this power saving mode), if you see it is light , just means it is in power saving mode
while the red light means if the battery in in charging .if it is red, it meaning the battery is in charging via USB, if not red , it means the battery not in charging, there is lots of cause for it is not in charging , maybe the USB is not connected , maybe the battery in full. notice when Quad in power up, the battery will not be charged , because the PC can only supply a current no more than 500mA, if the Quad is powered up , the LTC4054 can not charge the battry, so, even your battery is not full, it can not be charged(the red light is off)